When creating an online store, many merchants opt to use PayPal as their checkout of choice. Offering your buyers a PayPal checkout will likely increase your chance of sales since it is a well-known and trusted gateway. While having a buyer enter a specific code to receive a discount is a popular practice, as of 2010 it is still not supported by PayPal. But not to worry, there are ways around this.
Non-hosted Add to Cart Button
Ensure you are not using using a hosted “Add to Cart” button. In order to use a discount code, you must have a non-hosted button. To create one of these through PayPal, log into your PayPal account and click the “Merchant Services” tab.
Select “Merchant Tools.” In the “Website Payment Standard” section, choose the button you want to make.
Click “Create your button now” and fill out all fields. Then go to “Step 2: Track inventory” and uncheck the “Save button at PayPal” box.
Click “Create Button” and follow the “Remove code protection” link. At this point you will be able to see the unencrypted HTML code of the new button. Merely click “Select Code” and copy it to your website.
Ensure the script is capable of retrieving the discount code from the buyer, and then passing the new amount on to PayPal for payment.