Remove sold items

Unique items sold via PayPal can be automatically marked as sold.  This is a convenient way to prevent a unique item from being sold twice.
 

Check the item as unique


When the For sale and Price fields are switched on, there should be an Is unique checkbox next to each image. Check this.


Set-up IPN at PayPal


When IPN (Instant Payment Notification) is set-up within your PayPal account, unique items can only be purchased once.  Set-up IPN like so:

https://developer.paypal.com/docs/classic/ipn/integration-guide/IPNSetup/

When setting this up at PayPal your Notification URL will be:
https://yoursite.com/payment-notification

Replace yoursite.com in the URL above with your actual domain.