Hey everyone,

Just a quick post on how to block duplicate payments with PayPal. All you have to do is pass an invoice parameter and then select the ‘block multiple payments per invoice ID’ option in PayPal. I’ve attached an extract from PayPal’s documentation below:

1. Login at https://www.paypal.com
2. Click the ‘Profile’ subtab
3. Under ‘Selling Preferences’ click ‘Payment Receiving Preferences’
4. Choose ‘Yes, block multiple payments per invoice ID’ if you wish to utilize this feature while passing the “invoice” variable
5. Scroll to the bottom and click the ‘Save’ button

To pass the invoice number for Website Payments Standard, you will need to add a line of code to your existing button code. You cannot add this code to a button originally created as encrypted. Example below:

<input type=”hidden” name=”invoice” value=”001″>

The documentation is available at the following link:
https://ppmts.custhelp.com/app/answers/detail/a_id/165