diff --git a/changelog/7588-express-checkout-utilities b/changelog/7588-express-checkout-utilities
new file mode 100644
index 00000000000..143b670d60c
--- /dev/null
+++ b/changelog/7588-express-checkout-utilities
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Introduce WC_Payments_Express_Checkout_Button_Utils class.
diff --git a/includes/class-wc-payments-express-checkout-button-display-handler.php b/includes/class-wc-payments-express-checkout-button-display-handler.php
index ad8db375684..5a9cf2ec12c 100644
--- a/includes/class-wc-payments-express-checkout-button-display-handler.php
+++ b/includes/class-wc-payments-express-checkout-button-display-handler.php
@@ -35,17 +35,26 @@ class WC_Payments_Express_Checkout_Button_Display_Handler {
 	 */
 	private $platform_checkout_button_handler;
 
+	/**
+	 * Express Checkout Helper instance.
+	 *
+	 * @var WC_Payments_Express_Checkout_Button_Helper
+	 */
+	private $express_checkout_helper;
+
 	/**
 	 * Initialize class actions.
 	 *
 	 * @param WC_Payment_Gateway_WCPay                   $gateway WCPay gateway.
 	 * @param WC_Payments_Payment_Request_Button_Handler $payment_request_button_handler Payment request button handler.
 	 * @param WC_Payments_WooPay_Button_Handler          $platform_checkout_button_handler Platform checkout button handler.
+	 * @param WC_Payments_Express_Checkout_Button_Helper $express_checkout_helper Express checkout helper.
 	 */
-	public function __construct( WC_Payment_Gateway_WCPay $gateway, WC_Payments_Payment_Request_Button_Handler $payment_request_button_handler, WC_Payments_WooPay_Button_Handler $platform_checkout_button_handler ) {
+	public function __construct( WC_Payment_Gateway_WCPay $gateway, WC_Payments_Payment_Request_Button_Handler $payment_request_button_handler, WC_Payments_WooPay_Button_Handler $platform_checkout_button_handler, WC_Payments_Express_Checkout_Button_Helper $express_checkout_helper ) {
 		$this->gateway                          = $gateway;
 		$this->payment_request_button_handler   = $payment_request_button_handler;
 		$this->platform_checkout_button_handler = $platform_checkout_button_handler;
+		$this->express_checkout_helper           = $express_checkout_helper;
 
 		$this->platform_checkout_button_handler->init();
 		$this->payment_request_button_handler->init();
@@ -54,6 +63,8 @@ public function __construct( WC_Payment_Gateway_WCPay $gateway, WC_Payments_Paym
 		$is_payment_request_enabled = 'yes' === $this->gateway->get_option( 'payment_request' );
 
 		if ( $is_woopay_enabled || $is_payment_request_enabled ) {
+			add_action( 'wc_ajax_wcpay_add_to_cart', [ $this->express_checkout_helper, 'ajax_add_to_cart' ] );
+
 			add_action( 'woocommerce_after_add_to_cart_form', [ $this, 'display_express_checkout_buttons' ], 1 );
 			add_action( 'woocommerce_proceed_to_checkout', [ $this, 'display_express_checkout_buttons' ], 21 );
 			add_action( 'woocommerce_checkout_before_customer_details', [ $this, 'display_express_checkout_buttons' ], 1 );
diff --git a/includes/class-wc-payments-payment-request-button-handler.php b/includes/class-wc-payments-payment-request-button-handler.php
index ff030924969..7a30adad550 100644
--- a/includes/class-wc-payments-payment-request-button-handler.php
+++ b/includes/class-wc-payments-payment-request-button-handler.php
@@ -36,15 +36,24 @@ class WC_Payments_Payment_Request_Button_Handler {
 	 */
 	private $gateway;
 
+	/**
+	 * Express Checkout Helper instance.
+	 *
+	 * @var WC_Payments_Express_Checkout_Button_Helper
+	 */
+	private $express_checkout_helper;
+
 	/**
 	 * Initialize class actions.
 	 *
-	 * @param WC_Payments_Account      $account Account information.
-	 * @param WC_Payment_Gateway_WCPay $gateway WCPay gateway.
+	 * @param WC_Payments_Account                        $account Account information.
+	 * @param WC_Payment_Gateway_WCPay                   $gateway WCPay gateway.
+	 * @param WC_Payments_Express_Checkout_Button_Helper $express_checkout_helper Express checkout helper.
 	 */
-	public function __construct( WC_Payments_Account $account, WC_Payment_Gateway_WCPay $gateway ) {
-		$this->account = $account;
-		$this->gateway = $gateway;
+	public function __construct( WC_Payments_Account $account, WC_Payment_Gateway_WCPay $gateway, WC_Payments_Express_Checkout_Button_Helper $express_checkout_helper ) {
+		$this->account                 = $account;
+		$this->gateway                 = $gateway;
+		$this->express_checkout_helper = $express_checkout_helper;
 	}
 
 	/**
@@ -78,7 +87,6 @@ public function init() {
 		add_action( 'wc_ajax_wcpay_get_shipping_options', [ $this, 'ajax_get_shipping_options' ] );
 		add_action( 'wc_ajax_wcpay_update_shipping_method', [ $this, 'ajax_update_shipping_method' ] );
 		add_action( 'wc_ajax_wcpay_create_order', [ $this, 'ajax_create_order' ] );
-		add_action( 'wc_ajax_wcpay_add_to_cart', [ $this, 'ajax_add_to_cart' ] );
 		add_action( 'wc_ajax_wcpay_get_selected_product_data', [ $this, 'ajax_get_selected_product_data' ] );
 		add_action( 'wc_ajax_wcpay_pay_for_order', [ $this, 'ajax_pay_for_order' ] );
 
@@ -134,17 +142,6 @@ public function is_account_creation_possible() {
 		);
 	}
 
-	/**
-	 * Gets total label.
-	 *
-	 * @return string
-	 */
-	public function get_total_label() {
-		// Get statement descriptor from API/cached account data.
-		$statement_descriptor = $this->account->get_statement_descriptor();
-		return str_replace( "'", '', $statement_descriptor ) . apply_filters( 'wcpay_payment_request_total_label_suffix', ' (via WooCommerce)' );
-	}
-
 	/**
 	 * Sets the WC customer session if one is not set.
 	 * This is needed so nonces can be verified by AJAX Request.
@@ -211,7 +208,7 @@ public function get_button_height() {
 	 */
 	public function get_product_price( $product ) {
 		// If prices should include tax, using tax inclusive price.
-		if ( $this->cart_prices_include_tax() ) {
+		if ( $this->express_checkout_helper->cart_prices_include_tax() ) {
 			$base_price = wc_get_price_including_tax( $product );
 		} else {
 			$base_price = wc_get_price_excluding_tax( $product );
@@ -319,7 +316,7 @@ public function get_product_data() {
 
 		$data['displayItems'] = $items;
 		$data['total']        = [
-			'label'   => apply_filters( 'wcpay_payment_request_total_label', $this->get_total_label() ),
+			'label'   => apply_filters( 'wcpay_payment_request_total_label', $this->express_checkout_helper->get_total_label() ),
 			'amount'  => WC_Payments_Utils::prepare_amount( $price + $total_tax, $currency ),
 			'pending' => true,
 		];
@@ -382,7 +379,7 @@ public function display_pay_for_order_page_html( $order ) {
 		$data['displayItems']   = $items;
 		$data['needs_shipping'] = false; // This should be already entered/prepared.
 		$data['total']          = [
-			'label'   => apply_filters( 'wcpay_payment_request_total_label', $this->get_total_label() ),
+			'label'   => apply_filters( 'wcpay_payment_request_total_label', $this->express_checkout_helper->get_total_label() ),
 			'amount'  => WC_Payments_Utils::prepare_amount( $order->get_total(), $currency ),
 			'pending' => true,
 		];
@@ -400,7 +397,7 @@ public function get_cart_data() {
 			return false;
 		}
 
-		return $this->build_display_items();
+		return $this->express_checkout_helper->build_display_items();
 	}
 
 	/**
@@ -802,7 +799,7 @@ public function scripts() {
 			'is_pay_for_order'   => $this->is_pay_for_order_page(),
 			'has_block'          => has_block( 'woocommerce/cart' ) || has_block( 'woocommerce/checkout' ),
 			'product'            => $this->get_product_data(),
-			'total_label'        => $this->get_total_label(),
+			'total_label'        => $this->express_checkout_helper->get_total_label(),
 		];
 
 		WC_Payments::register_script_with_dependencies( 'WCPAY_PAYMENT_REQUEST', 'dist/payment-request', [ 'jquery', 'stripe' ] );
@@ -890,7 +887,7 @@ public function ajax_get_cart_details() {
 
 		WC()->cart->calculate_totals();
 
-		wp_send_json( array_merge( $this->build_display_items(), [ 'needs_shipping' => WC()->cart->needs_shipping() ] ) );
+		wp_send_json( array_merge( $this->express_checkout_helper->build_display_items(), [ 'needs_shipping' => WC()->cart->needs_shipping() ] ) );
 	}
 
 	/**
@@ -986,10 +983,10 @@ public function get_shipping_options( $shipping_address, $itemized_display_items
 
 			WC()->cart->calculate_totals();
 
-			$data          += $this->build_display_items( $itemized_display_items );
+			$data          += $this->express_checkout_helper->build_display_items( $itemized_display_items );
 			$data['result'] = 'success';
 		} catch ( Exception $e ) {
-			$data          += $this->build_display_items( $itemized_display_items );
+			$data          += $this->express_checkout_helper->build_display_items( $itemized_display_items );
 			$data['result'] = 'invalid_shipping_address';
 		}
 
@@ -1015,7 +1012,7 @@ public function ajax_update_shipping_method() {
 		$should_show_itemized_view = ! isset( $product_view_options['is_product_page'] ) ? true : filter_var( $product_view_options['is_product_page'], FILTER_VALIDATE_BOOLEAN );
 
 		$data           = [];
-		$data          += $this->build_display_items( $should_show_itemized_view );
+		$data          += $this->express_checkout_helper->build_display_items( $should_show_itemized_view );
 		$data['result'] = 'success';
 
 		wp_send_json( $data );
@@ -1121,7 +1118,7 @@ public function ajax_get_selected_product_data() {
 
 			$data['displayItems'] = $items;
 			$data['total']        = [
-				'label'   => $this->get_total_label(),
+				'label'   => $this->express_checkout_helper->get_total_label(),
 				'amount'  => WC_Payments_Utils::prepare_amount( $total + $total_tax, $currency ),
 				'pending' => true,
 			];
@@ -1139,62 +1136,6 @@ public function ajax_get_selected_product_data() {
 		}
 	}
 
-	/**
-	 * Adds the current product to the cart. Used on product detail page.
-	 */
-	public function ajax_add_to_cart() {
-		check_ajax_referer( 'wcpay-add-to-cart', 'security' );
-
-		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
-			define( 'WOOCOMMERCE_CART', true );
-		}
-
-		WC()->shipping->reset_shipping();
-
-		$product_id = isset( $_POST['product_id'] ) ? absint( $_POST['product_id'] ) : false;
-		$product    = wc_get_product( $product_id );
-
-		if ( ! $product ) {
-			wp_send_json(
-				[
-					'error' => [
-						'code'    => 'invalid_product_id',
-						'message' => __( 'Invalid product id', 'woocommerce-payments' ),
-					],
-				],
-				404
-			);
-			return;
-		}
-
-		$qty          = ! isset( $_POST['qty'] ) ? 1 : absint( $_POST['qty'] );
-		$product_type = $product->get_type();
-
-		// First empty the cart to prevent wrong calculation.
-		WC()->cart->empty_cart();
-
-		if ( ( 'variable' === $product_type || 'variable-subscription' === $product_type ) && isset( $_POST['attributes'] ) ) {
-			$attributes = wc_clean( wp_unslash( $_POST['attributes'] ) );
-
-			$data_store   = WC_Data_Store::load( 'product' );
-			$variation_id = $data_store->find_matching_product_variation( $product, $attributes );
-
-			WC()->cart->add_to_cart( $product->get_id(), $qty, $variation_id, $attributes );
-		}
-
-		if ( in_array( $product_type, [ 'simple', 'variation', 'subscription', 'subscription_variation' ], true ) ) {
-			WC()->cart->add_to_cart( $product->get_id(), $qty );
-		}
-
-		WC()->cart->calculate_totals();
-
-		$data           = [];
-		$data          += $this->build_display_items();
-		$data['result'] = 'success';
-
-		wp_send_json( $data );
-	}
-
 	/**
 	 * Handles payment requests on the Pay for Order page.
 	 *
@@ -1510,16 +1451,6 @@ protected function calculate_shipping( $address = [] ) {
 		WC()->shipping->calculate_shipping( $packages );
 	}
 
-	/**
-	 * Whether tax should be displayed on separate line in cart.
-	 * returns true if tax is disabled or display of tax in checkout is set to inclusive.
-	 *
-	 * @return boolean
-	 */
-	private function cart_prices_include_tax() {
-		return ! wc_tax_enabled() || 'incl' === get_option( 'woocommerce_tax_display_cart' );
-	}
-
 	/**
 	 * Builds the shipping methods to pass to Payment Request
 	 *
@@ -1544,103 +1475,6 @@ protected function build_shipping_methods( $shipping_methods ) {
 		return $shipping;
 	}
 
-	/**
-	 * Builds the line items to pass to Payment Request
-	 *
-	 * @param boolean $itemized_display_items Indicates whether to show subtotals or itemized views.
-	 */
-	public function build_display_items( $itemized_display_items = false ) {
-		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
-			define( 'WOOCOMMERCE_CART', true );
-		}
-
-		$items     = [];
-		$subtotal  = 0;
-		$discounts = 0;
-		$currency  = get_woocommerce_currency();
-
-		// Default show only subtotal instead of itemization.
-		if ( ! apply_filters( 'wcpay_payment_request_hide_itemization', true ) || $itemized_display_items ) {
-			foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
-				$amount         = $cart_item['line_subtotal'];
-				$subtotal      += $cart_item['line_subtotal'];
-				$quantity_label = 1 < $cart_item['quantity'] ? ' (x' . $cart_item['quantity'] . ')' : '';
-
-				$product_name = $cart_item['data']->get_name();
-
-				$item_tax = $this->cart_prices_include_tax() ? ( $cart_item['line_subtotal_tax'] ?? 0 ) : 0;
-
-				$item = [
-					'label'  => $product_name . $quantity_label,
-					'amount' => WC_Payments_Utils::prepare_amount( $amount + $item_tax, $currency ),
-				];
-
-				$items[] = $item;
-			}
-		}
-
-		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
-			$discounts = wc_format_decimal( WC()->cart->get_cart_discount_total(), WC()->cart->dp );
-		} else {
-			$applied_coupons = array_values( WC()->cart->get_coupon_discount_totals() );
-
-			foreach ( $applied_coupons as $amount ) {
-				$discounts += (float) $amount;
-			}
-		}
-
-		$discounts   = wc_format_decimal( $discounts, WC()->cart->dp );
-		$tax         = wc_format_decimal( WC()->cart->tax_total + WC()->cart->shipping_tax_total, WC()->cart->dp );
-		$shipping    = wc_format_decimal( WC()->cart->shipping_total, WC()->cart->dp );
-		$items_total = wc_format_decimal( WC()->cart->cart_contents_total, WC()->cart->dp ) + $discounts;
-		$order_total = version_compare( WC_VERSION, '3.2', '<' ) ? wc_format_decimal( $items_total + $tax + $shipping - $discounts, WC()->cart->dp ) : WC()->cart->get_total( '' );
-
-		if ( ! $this->cart_prices_include_tax() ) {
-			$items[] = [
-				'label'  => esc_html( __( 'Tax', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $tax, $currency ),
-			];
-		}
-
-		if ( WC()->cart->needs_shipping() ) {
-			$shipping_tax = $this->cart_prices_include_tax() ? WC()->cart->shipping_tax_total : 0;
-			$items[]      = [
-				'label'  => esc_html( __( 'Shipping', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $shipping + $shipping_tax, $currency ),
-			];
-		}
-
-		if ( WC()->cart->has_discount() ) {
-			$items[] = [
-				'label'  => esc_html( __( 'Discount', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $discounts, $currency ),
-			];
-		}
-
-		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
-			$cart_fees = WC()->cart->fees;
-		} else {
-			$cart_fees = WC()->cart->get_fees();
-		}
-
-		// Include fees and taxes as display items.
-		foreach ( $cart_fees as $key => $fee ) {
-			$items[] = [
-				'label'  => $fee->name,
-				'amount' => WC_Payments_Utils::prepare_amount( $fee->amount, $currency ),
-			];
-		}
-
-		return [
-			'displayItems' => $items,
-			'total'        => [
-				'label'   => $this->get_total_label(),
-				'amount'  => max( 0, apply_filters( 'wcpay_calculated_total', WC_Payments_Utils::prepare_amount( $order_total, $currency ), $order_total, WC()->cart ) ),
-				'pending' => false,
-			],
-		];
-	}
-
 	/**
 	 * Calculates whether Apple Pay is enabled for this store.
 	 * The option value is not stored in the database, and is calculated
@@ -1715,7 +1549,7 @@ public function get_login_confirmation_settings() {
 	 * @return array              An array of final taxes.
 	 */
 	private function get_taxes_like_cart( $product, $price ) {
-		if ( ! wc_tax_enabled() || $this->cart_prices_include_tax() ) {
+		if ( ! wc_tax_enabled() || $this->express_checkout_helper->cart_prices_include_tax() ) {
 			// Only proceed when taxes are enabled, but not included.
 			return [];
 		}
diff --git a/includes/class-wc-payments-woopay-button-handler.php b/includes/class-wc-payments-woopay-button-handler.php
index 44154c29ee7..5045174a7b3 100644
--- a/includes/class-wc-payments-woopay-button-handler.php
+++ b/includes/class-wc-payments-woopay-button-handler.php
@@ -125,8 +125,6 @@ public function init() {
 
 		add_filter( 'wcpay_payment_fields_js_config', [ $this, 'add_woopay_config' ] );
 
-		add_action( 'wc_ajax_wcpay_add_to_cart', [ $this, 'ajax_add_to_cart' ] );
-
 		add_action( 'wp_ajax_woopay_express_checkout_button_show_error_notice', [ $this, 'show_error_notice' ] );
 		add_action( 'wp_ajax_nopriv_woopay_express_checkout_button_show_error_notice', [ $this, 'show_error_notice' ] );
 	}
@@ -214,195 +212,6 @@ public function show_error_notice() {
 		wp_die();
 	}
 
-	/**
-	 * Adds the current product to the cart. Used on product detail page.
-	 */
-	public function ajax_add_to_cart() {
-		check_ajax_referer( 'wcpay-add-to-cart', 'security' );
-
-		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
-			define( 'WOOCOMMERCE_CART', true );
-		}
-
-		WC()->shipping->reset_shipping();
-
-		$product_id = isset( $_POST['product_id'] ) ? absint( $_POST['product_id'] ) : false;
-		$quantity   = ! isset( $_POST['quantity'] ) ? 1 : absint( $_POST['quantity'] );
-		$product    = wc_get_product( $product_id );
-
-		if ( ! $product ) {
-			wp_send_json(
-				[
-					'error' => [
-						'code'    => 'invalid_product_id',
-						'message' => __( 'Invalid product id', 'woocommerce-payments' ),
-					],
-				],
-				404
-			);
-			return;
-		}
-
-		$product_type = $product->get_type();
-
-		// First empty the cart to prevent wrong calculation.
-		WC()->cart->empty_cart();
-
-		$is_add_to_cart_valid = apply_filters( 'woocommerce_add_to_cart_validation', true, $product_id, $quantity );
-
-		if ( ! $is_add_to_cart_valid ) {
-			// Some extensions error messages needs to be
-			// submitted to show error messages.
-			wp_send_json(
-				[
-					'error'  => true,
-					'submit' => true,
-				],
-				400
-			);
-			return;
-		}
-
-		if ( ( 'variable' === $product_type || 'variable-subscription' === $product_type ) && isset( $_POST['attributes'] ) ) {
-			$attributes = wc_clean( wp_unslash( $_POST['attributes'] ) );
-
-			$data_store   = WC_Data_Store::load( 'product' );
-			$variation_id = $data_store->find_matching_product_variation( $product, $attributes );
-
-			WC()->cart->add_to_cart( $product->get_id(), $quantity, $variation_id, $attributes );
-		}
-
-		if ( in_array( $product_type, [ 'simple', 'subscription', 'subscription_variation', 'bundle', 'mix-and-match' ], true ) ) {
-			WC()->cart->add_to_cart( $product->get_id(), $quantity );
-		}
-
-		WC()->cart->calculate_totals();
-
-		$data           = [];
-		$data          += $this->build_display_items();
-		$data['result'] = 'success';
-
-		wp_send_json( $data );
-	}
-
-	/**
-	 * Builds the line items to pass to Payment Request
-	 *
-	 * @param boolean $itemized_display_items Indicates whether to show subtotals or itemized views.
-	 */
-	protected function build_display_items( $itemized_display_items = false ) {
-		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
-			define( 'WOOCOMMERCE_CART', true );
-		}
-
-		$items     = [];
-		$subtotal  = 0;
-		$discounts = 0;
-		$currency  = get_woocommerce_currency();
-
-		// Default show only subtotal instead of itemization.
-		if ( ! apply_filters( 'wcpay_payment_request_hide_itemization', true ) || $itemized_display_items ) {
-			foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
-				$amount         = $cart_item['line_subtotal'];
-				$subtotal      += $cart_item['line_subtotal'];
-				$quantity_label = 1 < $cart_item['quantity'] ? ' (x' . $cart_item['quantity'] . ')' : '';
-
-				$product_name = $cart_item['data']->get_name();
-
-				$item_tax = $this->cart_prices_include_tax() ? ( $cart_item['line_subtotal_tax'] ?? 0 ) : 0;
-
-				$item = [
-					'label'  => $product_name . $quantity_label,
-					'amount' => WC_Payments_Utils::prepare_amount( $amount + $item_tax, $currency ),
-				];
-
-				$items[] = $item;
-			}
-		}
-
-		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
-			$discounts = wc_format_decimal( WC()->cart->get_cart_discount_total(), WC()->cart->dp );
-		} else {
-			$applied_coupons = array_values( WC()->cart->get_coupon_discount_totals() );
-
-			foreach ( $applied_coupons as $amount ) {
-				$discounts += (float) $amount;
-			}
-		}
-
-		$discounts   = wc_format_decimal( $discounts, WC()->cart->dp );
-		$tax         = wc_format_decimal( WC()->cart->tax_total + WC()->cart->shipping_tax_total, WC()->cart->dp );
-		$shipping    = wc_format_decimal( WC()->cart->shipping_total, WC()->cart->dp );
-		$items_total = wc_format_decimal( WC()->cart->cart_contents_total, WC()->cart->dp ) + $discounts;
-		$order_total = version_compare( WC_VERSION, '3.2', '<' ) ? wc_format_decimal( $items_total + $tax + $shipping - $discounts, WC()->cart->dp ) : WC()->cart->get_total( '' );
-
-		if ( ! $this->cart_prices_include_tax() ) {
-			$items[] = [
-				'label'  => esc_html( __( 'Tax', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $tax, $currency ),
-			];
-		}
-
-		if ( WC()->cart->needs_shipping() ) {
-			$shipping_tax = $this->cart_prices_include_tax() ? WC()->cart->shipping_tax_total : 0;
-			$items[]      = [
-				'label'  => esc_html( __( 'Shipping', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $shipping + $shipping_tax, $currency ),
-			];
-		}
-
-		if ( WC()->cart->has_discount() ) {
-			$items[] = [
-				'label'  => esc_html( __( 'Discount', 'woocommerce-payments' ) ),
-				'amount' => WC_Payments_Utils::prepare_amount( $discounts, $currency ),
-			];
-		}
-
-		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
-			$cart_fees = WC()->cart->fees;
-		} else {
-			$cart_fees = WC()->cart->get_fees();
-		}
-
-		// Include fees and taxes as display items.
-		foreach ( $cart_fees as $key => $fee ) {
-			$items[] = [
-				'label'  => $fee->name,
-				'amount' => WC_Payments_Utils::prepare_amount( $fee->amount, $currency ),
-			];
-		}
-
-		return [
-			'displayItems' => $items,
-			'total'        => [
-				'label'   => $this->get_total_label(),
-				'amount'  => max( 0, apply_filters( 'wcpay_calculated_total', WC_Payments_Utils::prepare_amount( $order_total, $currency ), $order_total, WC()->cart ) ),
-				'pending' => false,
-			],
-		];
-	}
-
-	/**
-	 * Whether tax should be displayed on separate line in cart.
-	 * returns true if tax is disabled or display of tax in checkout is set to inclusive.
-	 *
-	 * @return boolean
-	 */
-	private function cart_prices_include_tax() {
-		return ! wc_tax_enabled() || 'incl' === get_option( 'woocommerce_tax_display_cart' );
-	}
-
-	/**
-	 * Gets total label.
-	 *
-	 * @return string
-	 */
-	public function get_total_label() {
-		// Get statement descriptor from API/cached account data.
-		$statement_descriptor = $this->account->get_statement_descriptor();
-		return str_replace( "'", '', $statement_descriptor ) . apply_filters( 'wcpay_payment_request_total_label_suffix', ' (via WooCommerce)' );
-	}
-
 	/**
 	 * Checks if this is a product page or content contains a product_page shortcode.
 	 *
diff --git a/includes/class-wc-payments.php b/includes/class-wc-payments.php
index baf1ea9a8ca..bd0cb8dc97f 100644
--- a/includes/class-wc-payments.php
+++ b/includes/class-wc-payments.php
@@ -295,6 +295,13 @@ class WC_Payments {
 	 */
 	private static $incentives_service;
 
+	/**
+	 * Instance of WC_Payments_Express_Checkout_Button_Helper, created in init function.
+	 *
+	 * @var WC_Payments_Express_Checkout_Button_Helper
+	 */
+	private static $express_checkout_helper;
+
 	/**
 	 * Instance of Compatibility_Service, created in init function
 	 *
@@ -415,6 +422,7 @@ public static function init() {
 		include_once __DIR__ . '/payment-methods/class-affirm-payment-method.php';
 		include_once __DIR__ . '/payment-methods/class-afterpay-payment-method.php';
 		include_once __DIR__ . '/payment-methods/class-klarna-payment-method.php';
+		include_once __DIR__ . '/express-checkout/class-wc-payments-express-checkout-button-helper.php';
 		include_once __DIR__ . '/class-wc-payment-token-wcpay-sepa.php';
 		include_once __DIR__ . '/class-wc-payments-status.php';
 		include_once __DIR__ . '/class-wc-payments-token-service.php';
@@ -501,6 +509,7 @@ public static function init() {
 		self::$failed_transaction_rate_limiter      = new Session_Rate_Limiter( Session_Rate_Limiter::SESSION_KEY_DECLINED_CARD_REGISTRY, 5, 10 * MINUTE_IN_SECONDS );
 		self::$order_success_page                   = new WC_Payments_Order_Success_Page();
 		self::$onboarding_service                   = new WC_Payments_Onboarding_Service( self::$api_client, self::$database_cache );
+		self::$express_checkout_helper              = new WC_Payments_Express_Checkout_Button_Helper( self::$account );
 		self::$woopay_util                          = new WooPay_Utilities();
 		self::$woopay_tracker                       = new WooPay_Tracker( self::get_wc_payments_http() );
 		self::$incentives_service                   = new WC_Payments_Incentives_Service( self::$database_cache );
@@ -1504,9 +1513,9 @@ function ( $container ) {
 	 */
 	public static function maybe_display_express_checkout_buttons() {
 		if ( WC_Payments_Features::are_payments_enabled() ) {
-			$payment_request_button_handler          = new WC_Payments_Payment_Request_Button_Handler( self::$account, self::get_gateway() );
+			$payment_request_button_handler          = new WC_Payments_Payment_Request_Button_Handler( self::$account, self::get_gateway(), self::$express_checkout_helper );
 			$woopay_button_handler                   = new WC_Payments_WooPay_Button_Handler( self::$account, self::get_gateway(), self::$woopay_util );
-			$express_checkout_button_display_handler = new WC_Payments_Express_Checkout_Button_Display_Handler( self::get_gateway(), $payment_request_button_handler, $woopay_button_handler );
+			$express_checkout_button_display_handler = new WC_Payments_Express_Checkout_Button_Display_Handler( self::get_gateway(), $payment_request_button_handler, $woopay_button_handler, self::$express_checkout_helper );
 		}
 	}
 
diff --git a/includes/express-checkout/class-wc-payments-express-checkout-button-helper.php b/includes/express-checkout/class-wc-payments-express-checkout-button-helper.php
new file mode 100644
index 00000000000..1eb77586ebb
--- /dev/null
+++ b/includes/express-checkout/class-wc-payments-express-checkout-button-helper.php
@@ -0,0 +1,235 @@
+<?php
+/**
+ * Class WC_Payments_Express_Checkout_Button_Helper
+ *
+ * @package WooCommerce\Payments
+ */
+
+defined( 'ABSPATH' ) || exit;
+
+/**
+ * Express Checkout Button Helper class.
+ */
+class WC_Payments_Express_Checkout_Button_Helper {
+	/**
+	 * WC_Payments_Account instance to get information about the account
+	 *
+	 * @var WC_Payments_Account
+	 */
+	private $account;
+
+	/**
+	 * Initialize class actions.
+	 *
+	 * @param WC_Payments_Account $account Account information.
+	 */
+	public function __construct( WC_Payments_Account $account ) {
+		$this->account = $account;
+	}
+
+	/**
+	 * Adds the current product to the cart. Used on product detail page.
+	 */
+	public function ajax_add_to_cart() {
+		check_ajax_referer( 'wcpay-add-to-cart', 'security' );
+
+		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
+			define( 'WOOCOMMERCE_CART', true );
+		}
+
+		WC()->shipping->reset_shipping();
+
+		$product_id = isset( $_POST['product_id'] ) ? absint( $_POST['product_id'] ) : false;
+		$product    = wc_get_product( $product_id );
+
+		if ( ! $product ) {
+			wp_send_json(
+				[
+					'error' => [
+						'code'    => 'invalid_product_id',
+						'message' => __( 'Invalid product id', 'woocommerce-payments' ),
+					],
+				],
+				404
+			);
+			return;
+		}
+
+		$quantity = $this->get_quantity();
+
+		$product_type = $product->get_type();
+
+		$is_add_to_cart_valid = apply_filters( 'woocommerce_add_to_cart_validation', true, $product_id, $quantity );
+
+		if ( ! $is_add_to_cart_valid ) {
+			// Some extensions error messages needs to be
+			// submitted to show error messages.
+			wp_send_json(
+				[
+					'error'  => true,
+					'submit' => true,
+				],
+				400
+			);
+			return;
+		}
+
+		// First empty the cart to prevent wrong calculation.
+		WC()->cart->empty_cart();
+
+		if ( ( 'variable' === $product_type || 'variable-subscription' === $product_type ) && isset( $_POST['attributes'] ) ) {
+			$attributes = wc_clean( wp_unslash( $_POST['attributes'] ) );
+
+			$data_store   = WC_Data_Store::load( 'product' );
+			$variation_id = $data_store->find_matching_product_variation( $product, $attributes );
+
+			WC()->cart->add_to_cart( $product->get_id(), $quantity, $variation_id, $attributes );
+		}
+
+		if ( in_array( $product_type, [ 'simple', 'subscription', 'subscription_variation', 'bundle', 'mix-and-match' ], true ) ) {
+			WC()->cart->add_to_cart( $product->get_id(), $quantity );
+		}
+
+		WC()->cart->calculate_totals();
+
+		$data           = [];
+		$data          += $this->build_display_items();
+		$data['result'] = 'success';
+
+		wp_send_json( $data );
+	}
+
+	/**
+	 * Builds the line items to pass to Payment Request
+	 *
+	 * @param boolean $itemized_display_items Indicates whether to show subtotals or itemized views.
+	 */
+	public function build_display_items( $itemized_display_items = false ) {
+		if ( ! defined( 'WOOCOMMERCE_CART' ) ) {
+			define( 'WOOCOMMERCE_CART', true );
+		}
+
+		$items     = [];
+		$subtotal  = 0;
+		$discounts = 0;
+		$currency  = get_woocommerce_currency();
+
+		// Default show only subtotal instead of itemization.
+		if ( ! apply_filters( 'wcpay_payment_request_hide_itemization', true ) || $itemized_display_items ) {
+			foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
+				$amount         = $cart_item['line_subtotal'];
+				$subtotal      += $cart_item['line_subtotal'];
+				$quantity_label = 1 < $cart_item['quantity'] ? ' (x' . $cart_item['quantity'] . ')' : '';
+
+				$product_name = $cart_item['data']->get_name();
+
+				$item_tax = $this->cart_prices_include_tax() ? ( $cart_item['line_subtotal_tax'] ?? 0 ) : 0;
+
+				$item = [
+					'label'  => $product_name . $quantity_label,
+					'amount' => WC_Payments_Utils::prepare_amount( $amount + $item_tax, $currency ),
+				];
+
+				$items[] = $item;
+			}
+		}
+
+		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
+			$discounts = wc_format_decimal( WC()->cart->get_cart_discount_total(), WC()->cart->dp );
+		} else {
+			$applied_coupons = array_values( WC()->cart->get_coupon_discount_totals() );
+
+			foreach ( $applied_coupons as $amount ) {
+				$discounts += (float) $amount;
+			}
+		}
+
+		$discounts   = wc_format_decimal( $discounts, WC()->cart->dp );
+		$tax         = wc_format_decimal( WC()->cart->tax_total + WC()->cart->shipping_tax_total, WC()->cart->dp );
+		$shipping    = wc_format_decimal( WC()->cart->shipping_total, WC()->cart->dp );
+		$items_total = wc_format_decimal( WC()->cart->cart_contents_total, WC()->cart->dp ) + $discounts;
+		$order_total = version_compare( WC_VERSION, '3.2', '<' ) ? wc_format_decimal( $items_total + $tax + $shipping - $discounts, WC()->cart->dp ) : WC()->cart->get_total( '' );
+
+		if ( ! $this->cart_prices_include_tax() ) {
+			$items[] = [
+				'label'  => esc_html( __( 'Tax', 'woocommerce-payments' ) ),
+				'amount' => WC_Payments_Utils::prepare_amount( $tax, $currency ),
+			];
+		}
+
+		if ( WC()->cart->needs_shipping() ) {
+			$shipping_tax = $this->cart_prices_include_tax() ? WC()->cart->shipping_tax_total : 0;
+			$items[]      = [
+				'label'  => esc_html( __( 'Shipping', 'woocommerce-payments' ) ),
+				'amount' => WC_Payments_Utils::prepare_amount( $shipping + $shipping_tax, $currency ),
+			];
+		}
+
+		if ( WC()->cart->has_discount() ) {
+			$items[] = [
+				'label'  => esc_html( __( 'Discount', 'woocommerce-payments' ) ),
+				'amount' => WC_Payments_Utils::prepare_amount( $discounts, $currency ),
+			];
+		}
+
+		if ( version_compare( WC_VERSION, '3.2', '<' ) ) {
+			$cart_fees = WC()->cart->fees;
+		} else {
+			$cart_fees = WC()->cart->get_fees();
+		}
+
+		// Include fees and taxes as display items.
+		foreach ( $cart_fees as $key => $fee ) {
+			$items[] = [
+				'label'  => $fee->name,
+				'amount' => WC_Payments_Utils::prepare_amount( $fee->amount, $currency ),
+			];
+		}
+
+		return [
+			'displayItems' => $items,
+			'total'        => [
+				'label'   => $this->get_total_label(),
+				'amount'  => max( 0, apply_filters( 'wcpay_calculated_total', WC_Payments_Utils::prepare_amount( $order_total, $currency ), $order_total, WC()->cart ) ),
+				'pending' => false,
+			],
+		];
+	}
+
+	/**
+	 * Whether tax should be displayed on separate line in cart.
+	 * returns true if tax is disabled or display of tax in checkout is set to inclusive.
+	 *
+	 * @return boolean
+	 */
+	public function cart_prices_include_tax() {
+		return ! wc_tax_enabled() || 'incl' === get_option( 'woocommerce_tax_display_cart' );
+	}
+
+	/**
+	 * Gets total label.
+	 *
+	 * @return string
+	 */
+	public function get_total_label() {
+		// Get statement descriptor from API/cached account data.
+		$statement_descriptor = $this->account->get_statement_descriptor();
+		return str_replace( "'", '', $statement_descriptor ) . apply_filters( 'wcpay_payment_request_total_label_suffix', ' (via WooCommerce)' );
+	}
+
+	/**
+	 * Gets quantity from request.
+	 *
+	 * @return int
+	 */
+	private function get_quantity() {
+		// Payment Request Button sends the quantity as qty. WooPay sends it as quantity.
+		if ( isset( $_POST['quantity'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Missing
+			return absint( $_POST['quantity'] ); // phpcs:ignore WordPress.Security.NonceVerification.Missing
+		} elseif ( isset( $_POST['qty'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Missing
+			return absint( $_POST['qty'] ); // phpcs:ignore WordPress.Security.NonceVerification.Missing
+		} else {
+			return 1;
+		}
+	}
+}
diff --git a/tests/unit/test-class-wc-payments-express-checkout-button-display-handler.php b/tests/unit/test-class-wc-payments-express-checkout-button-display-handler.php
index 220f3d2ff03..dfb059ba7b4 100644
--- a/tests/unit/test-class-wc-payments-express-checkout-button-display-handler.php
+++ b/tests/unit/test-class-wc-payments-express-checkout-button-display-handler.php
@@ -63,6 +63,13 @@ class WC_Payments_Express_Checkout_Button_Display_Handler_Test extends WCPAY_Uni
 	 */
 	private $mock_woopay_utilities;
 
+	/**
+	 * Express Checkout Helper instance.
+	 *
+	 * @var WC_Payments_Express_Checkout_Button_Helper
+	 */
+	private $express_checkout_helper;
+
 	/**
 	 * Sets up things all tests need.
 	 */
@@ -103,11 +110,14 @@ public function set_up() {
 			)
 			->getMock();
 
+		$this->express_checkout_helper = new WC_Payments_Express_Checkout_Button_Helper( $this->mock_wcpay_account );
+
 		$this->mock_payment_request_button_handler = $this->getMockBuilder( WC_Payments_Payment_Request_Button_Handler::class )
 			->setConstructorArgs(
 				[
 					$this->mock_wcpay_account,
 					$this->mock_wcpay_gateway,
+					$this->express_checkout_helper,
 				]
 			)
 			->setMethods(
@@ -118,7 +128,7 @@ public function set_up() {
 			)
 			->getMock();
 
-			$this->express_checkout_button_display_handler = new WC_Payments_Express_Checkout_Button_Display_Handler( $this->mock_wcpay_gateway, $this->mock_payment_request_button_handler, $this->mock_woopay_button_handler );
+			$this->express_checkout_button_display_handler = new WC_Payments_Express_Checkout_Button_Display_Handler( $this->mock_wcpay_gateway, $this->mock_payment_request_button_handler, $this->mock_woopay_button_handler, $this->express_checkout_helper );
 
 		add_filter(
 			'woocommerce_available_payment_gateways',
diff --git a/tests/unit/test-class-wc-payments-payment-request-button-handler.php b/tests/unit/test-class-wc-payments-payment-request-button-handler.php
index 7940d7b20f0..ce1283265b4 100644
--- a/tests/unit/test-class-wc-payments-payment-request-button-handler.php
+++ b/tests/unit/test-class-wc-payments-payment-request-button-handler.php
@@ -76,6 +76,13 @@ class WC_Payments_Payment_Request_Button_Handler_Test extends WCPAY_UnitTestCase
 	 */
 	private $mock_wcpay_gateway;
 
+	/**
+	 * Express Checkout Helper instance.
+	 *
+	 * @var WC_Payments_Express_Checkout_Button_Helper
+	 */
+	private $express_checkout_helper;
+
 	/**
 	 * Sets up things all tests need.
 	 */
@@ -100,7 +107,9 @@ public function set_up() {
 
 		$this->mock_wcpay_gateway = $this->make_wcpay_gateway();
 
-		$this->pr = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway );
+		$this->express_checkout_helper = new WC_Payments_Express_Checkout_Button_Helper( $this->mock_wcpay_account );
+
+		$this->pr = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway, $this->express_checkout_helper );
 
 		$this->simple_product = WC_Helper_Product::create_simple_product();
 
@@ -294,7 +303,7 @@ public function test_get_shipping_options_keeps_chosen_option() {
 
 	public function test_get_button_settings() {
 		$this->mock_wcpay_gateway = $this->make_wcpay_gateway();
-		$this->pr                 = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway );
+		$this->pr                 = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway, $this->express_checkout_helper );
 
 		$this->assertEquals(
 			[
@@ -320,7 +329,7 @@ function() {
 			}
 		);
 		$this->mock_wcpay_gateway = $this->make_wcpay_gateway();
-		$this->pr                 = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway );
+		$this->pr                 = new WC_Payments_Payment_Request_Button_Handler( $this->mock_wcpay_account, $this->mock_wcpay_gateway, $this->express_checkout_helper );
 
 		$this->assertFalse( $this->pr->has_allowed_items_in_cart() );
 	}
@@ -505,10 +514,10 @@ public function test_get_product_data_returns_the_same_as_build_display_items_wi
 		add_filter( 'pre_option_woocommerce_tax_display_cart', [ $this, "__return_$tax_display_cart" ] ); // reset in tear_down.
 		add_filter( 'wc_shipping_enabled', '__return_false' ); // reset in tear_down.
 		WC()->cart->calculate_totals();
-		$build_display_items_result = $this->pr->build_display_items( true );
+		$build_display_items_result = $this->express_checkout_helper->build_display_items( true );
 
 		$mock_pr = $this->getMockBuilder( WC_Payments_Payment_Request_Button_Handler::class )
-			->setConstructorArgs( [ $this->mock_wcpay_account, $this->mock_wcpay_gateway ] )
+			->setConstructorArgs( [ $this->mock_wcpay_account, $this->mock_wcpay_gateway, $this->express_checkout_helper ] )
 			->setMethods( [ 'is_product', 'get_product' ] )
 			->getMock();