diff --git a/sdi/README.md b/sdi/README.md
index ef711dc..57e9f14 100644
--- a/sdi/README.md
+++ b/sdi/README.md
@@ -26,6 +26,54 @@ After logging in, we have access to the following options:
 - View service agreement
 - Change Endpoint
 
+## Send an invoice
+
+To send an invoice you need:
+- invoice file in XML format
+- file with CA certificates in PEM format
+- PEM certificate (see the Certificato_Client folder)
+- PEM RSA private key (generated during initial registration process)
+
+Example of use:
+
+```console
+$ go run ./cmd/gobl.fatturapa transmit --ca-cert ./ca-all.pem --cert ./SDI-B85905495.pem --key ./key_client.key --verbose --env test invoice.xml
+2024/05/28 17:00:00.000000 DEBUG RESTY
+==============================================================================
+~~~ REQUEST ~~~
+POST  /ricevi_file  HTTP/1.1
+HOST   : testservizi.fatturapa.it
+HEADERS:
+	Content-Type: text/plain; charset=utf-8
+	User-Agent: go-resty/2.13.1 (https://github.com/go-resty/resty)
+BODY   :
+<?xml version='1.0' encoding='UTF-8'?><soapenv:Envelope xmlns:soapenv='http://schemas.xmlsoap.org/soap/envelope/' xmlns:typ='http://www.fatturapa.gov.it/sdi/ws/trasmissione/v1.0/types'><soapenv:Header/><soapenv:Body><typ:fileSdIAccoglienza><NomeFile>invoice.xml</NomeFile><File>FILE CONTENT</File></typ:fileSdIAccoglienza></soapenv:Body></soapenv:Envelope>
+------------------------------------------------------------------------------
+~~~ RESPONSE ~~~
+STATUS       : 200 OK
+PROTO        : HTTP/1.1
+RECEIVED AT  : 2024-05-28T17:00:00.500000000+02:00
+TIME DURATION: 500.000000ms
+HEADERS      :
+	Cache-Control: no-cache="set-cookie, set-cookie2"
+	Content-Language: en-US
+	Content-Length: 716
+	Content-Type: multipart/related; boundary="MIMEBoundary_"; type="application/xop+xml"; start="<0.182152212d14b303688146ac0db42b507ac086a479534824@apache.org>"; start-info="text/xml"
+	Date: Tue, 28 May 2024 15:00:00 GMT
+	Expires: Thu, 01 Dec 1994 16:00:00 GMT
+	Set-Cookie: ==; HTTPOnly; Path=/; Domain=.fatturapa.it; HttpOnly
+	X-Powered-By: Servlet/3.0
+BODY         :
+--MIMEBoundary_
+Content-Type: application/xop+xml; charset=utf-8; type="text/xml"
+Content-Transfer-Encoding: binary
+Content-ID: <0.182152212d14b303688146ac0db42b507ac086a479534824@apache.org>
+
+<?xml version="1.0" encoding="utf-8"?><soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"><soapenv:Body><ns2:rispostaSdIRiceviFile xmlns:ns2="http://www.fatturapa.gov.it/sdi/ws/trasmissione/v1.0/types"><IdentificativoSdI>29208092</IdentificativoSdI><DataOraRicezione>2024-05-28T17:00:00.200+02:00</DataOraRicezione></ns2:rispostaSdIRiceviFile></soapenv:Body></soapenv:Envelope>
+--MIMEBoundary_--
+==============================================================================
+```
+
 ## Links
 
 - [Manage the channel](https://sdi.fatturapa.gov.it/SdI2FatturaPAWebSpa/GestireCanaleAction.do)