diff --git a/README.md b/README.md
index c5f0c6c..e71706c 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ gr4vy-ios doesn't contain any external dependencies.
 use_frameworks!
 
 target 'YOUR_TARGET_NAME' do
-    pod 'gr4vy-ios', '2.2.0'
+    pod 'gr4vy-ios', '2.2.1'
 end
 ```
 
@@ -131,7 +131,7 @@ These are the parameteres available on the `launch` method:
 | `intent`                  | `Optional` | `authorize`, `capture` - Defines the intent of this API call. This determines the desired initial state of the transaction.|
 | `metadata`                | `Optional` | An optional dictionary of key/values for transaction metadata. All values should be a string.|
 | `paymentSource`           | `Optional` | `installment`, `recurring` - Can be used to signal that Embed is used to capture the first transaction for a subscription or an installment. When used, `store` is implied to be `true` and `display` is implied to be `supportsTokenization`. This means that payment options that do not support tokenization are automatically hidden. |
-| `cartItems`               | `Optional` | An optional array of cart item objects, each object must define a `name`, `quantity`, and `unitAmount`.|
+| `cartItems`               | `Optional` | An optional array of cart item objects, each object must define a `name`, `quantity`, and `unitAmount`. Other optional properties are `discountAmount`, `taxAmount`, `externalIdentifier`, `sku`, `productUrl`, `imageUrl`, `categories` and `productType`.|
 | `environment`| `Optional`       | `.sandbox`, `.production`. Defaults to `.production`. When `.sandbox` is provided the URL will contain `sandbox.GR4VY_ID`. |
 | `applePayMerchantId`| `Optional`       | The Apple merchant ID to be used during Apple Pay transcations |
 | `applePayMerchantName`| `Optional`       | The name which appears in the Apple Pay dialog next to "Pay" |
diff --git a/gr4vy-iOS/Models/Gr4vyCartItem.swift b/gr4vy-iOS/Models/Gr4vyCartItem.swift
index 314a6af..b603559 100644
--- a/gr4vy-iOS/Models/Gr4vyCartItem.swift
+++ b/gr4vy-iOS/Models/Gr4vyCartItem.swift
@@ -9,8 +9,8 @@ public struct Gr4vyCartItem: Codable {
     let name: String
     let quantity: Int
     let unitAmount: Int
-    let discountAmount: Int
-    let taxAmount: Int
+    let discountAmount: Int?
+    let taxAmount: Int?
     var externalIdentifier:String? = nil
     var sku: String? = nil
     var productUrl: String? = nil
@@ -18,7 +18,7 @@ public struct Gr4vyCartItem: Codable {
     var categories: [String]? = nil
     var productType: String? = nil
     
-    public init(name: String, quantity: Int, unitAmount: Int, discountAmount: Int = 0, taxAmount: Int = 0,
+    public init(name: String, quantity: Int, unitAmount: Int, discountAmount: Int? = 0, taxAmount: Int? = 0,
                 externalIdentifier: String? = nil, sku: String? = nil, productUrl: String? = nil, imageUrl: String? = nil, categories: [String]? = nil, productType: String? = nil) {
         self.name = name
         self.quantity = quantity
diff --git a/gr4vy-ios.podspec b/gr4vy-ios.podspec
index c4e458c..303e219 100644
--- a/gr4vy-ios.podspec
+++ b/gr4vy-ios.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name = 'gr4vy-ios'
-  s.version = '2.2.0'
+  s.version = '2.2.1'
   s.license = 'MIT'
   s.summary = 'Quickly embed Gr4vy in your iOS app to store card details, authorize payments, and capture a transaction.'
   s.homepage = 'https://github.com/gr4vy/gr4vy-ios'