Paypal error on checkout "This invoice has already been paid"

Who is this article for?

This information applies to any Webninja customers who are using Paypal as their payment method.

Symptom:

the customer attempts to checkout using Paypal as the payment method and is redirected to Paypal's site to make the payment.

When they attempt to make the payment, they're confronted with an error stating:

This invoice has already been paid

and they cannot proceed further - resulting in a lost sale!

Solution:

in your Paypal Merchant settings - you can make this update:
(NOTE: this is not for the end-user customer to do in their Paypal - you as the merchant/seller receiving the payment need to make this change in your Paypal settings)

Steps to resolve:

1. Log into your PayPal business account on paypal.com.

2.  Click the settings icon at the top of your PayPal account page and then click Profile and settings.

   Click My selling tools.

   Note: If you do not see the profile icon at the top of the page, click Profile, which appears in the top menu when the My Account tab is selected, and then click My selling tools.

3. Click Update next to  Block payments  in the Getting paid and managing my risk section.

4. Scroll down the page to the Block accidental payments  setting, and select the following option:

   • No, allow multiple payments per invoice ID  – Do not limit the number of payments received for an invoice. Choosing this option might result in duplicate payments that require a refund.

5. Scroll to the bottom of the page and click Save.

This will prevent the error from popping up again for any further customers.

Instructions sourced from Paypal's support here: