Due to restrictions enforced by PayPal, it's not currently possible to create an s2Member Pro Form Coupon Code for a 100% discount because PayPal requires the checkout to total at least $0.01.

To get around this, you can use an s2Member Free Registration Form (s2Member Pro required) to allow your visitors to register without paying.

You can generate a Free Registration Form from WP Admin -> s2Member -> PayPal Pro Forms -> PayPal Pro / Free Registration Forms

Restricting Access to the Free Registration Form

To help prevent unauthorized access to the Free Registration Form, you have a few options.

1. Use a voucher/coupon code in the URL and check to see if the code is present and valid before displaying the Free Registration Form.
2. Create a custom HTML form that accepts a voucher/coupon code and then write custom PHP code to check the code against a known-list of codes, only providing access to the form if the code is valid.

While the second option provides more flexibility and helps prevent the sharing/reuse of the code, it requires more custom programming. In this article, I will explain how to accomplish the easier of the two methods: Using a voucher/coupon code in the page URL and displaying the Free Registration Form if the code is present.

For example, if your purchase page is located at http://example.com/purchase/, then visitors will need to use http://example.com/purchase/?voucher=free to display the Free Registration Form. (You can change free to anything you like in the PHP code that you add to the page; see below.)

Verifying the Voucher/Coupon Code using PHP

Use the following PHP code on your purchase page to check if the page URL contains the voucher/coupon code. If the URL contains the correct code, the Free Registration Form will be displayed. Otherwise, the normal payment form will be displayed.

<?php if (isset($_GET['voucher']) && $_GET['voucher'] == 'free') { ?>
	Show the free registration form.
<?php } else { ?>
	Show the payment form.
<?php } ?>