In order to receive payments for User Upgrades, you must have a Premier or Business PayPal account. You must enable Instant Payment Notifications (IPNs) in PayPal under your Selling Preferences. You should enter a notification URL of [your Board URL]/payment_callback.php.
Paypal sends a callback to the payment_callback.php file in your forum directory. The callback is logged in the xf_user_upgrade_log table in the database.Thanks for the info. That's what I was looking for. When you run a business each and every transaction made in the company should be registered as a verification (certain rules apply how a verification should be made) in the accounting. How does that work when you use Paypal?