You can enable the option to use discounts from within payment forms for all users. For instance, if you have a 50% discount code enabled, your users can input it in the required field of the form to avail said discount. 

Adding Discount Inputs to Payment Forms

1

First, head to the  GetPaid > Payment Forms section, and then click Add New. 

2

The  Add New Payment Form page features a drag and drop builder. Locate the Discount Input field, and add it to your payment form. Save your form. 

All done! Now, when your users use this form to checkout, they can type in the discount coupon codes in the relevant field and GetPaid will take care of the rest.