After your payment you can retrieve your invoice directly from your user account.

Log in to TargetEZ and go to User Account by clicking on "Hello, [your email]" then click on "Personal Information".

In the "My Invoices" section

You have the list of your invoices. Click on the button "Download Invoice". 

A new window will open containing your invoice.

You can print or download it by clicking on the corresponding buttons at the bottom of the page.

A print window will open and to save the document as a .PDF file, simply select "Save as PDF" in the destination.