Order forms are where a form builder either saves you a plugin or sends you looking for one. Here is how to build one in SubtleForms 2.1.
1. Add what you sell
Use a Product field for a single item with a quantity, Priced Options for choices like ticket types, Custom Amount for donations, and Fixed Fee for something like a booking fee.
2. Show the order
Add an Order Summary field. It lists each line, the subtotal, any discount, tax and the total, and updates as the visitor makes choices.
3. Create a coupon
Open Subtle Forms > Payments and add a coupon. Choose a percent or fixed discount, then add any rules you need: a minimum order, a usage limit, start and end dates, or the forms it works on.
4. Take the payment
With SubtleForms Pro, connect Stripe to accept cards, Apple Pay and Google Pay. The card is authorised on submit and captured after the entry is saved. Without Pro, the order is saved with the entry as payment pending, ready for an offline payment.
The full walkthrough is in the docs: Payments and coupons.