Are you able to reimburse a customer using a discount code after the fact of their purchase?

I’m building an ecommerce store for a client and am wanting to know if we can apply discounts to orders that have already been made ultimately reimbursing a customer. We created a discount code for her clients who had been there to support her business from the start, one of them forgot to enter the code. Rather than just refunding, I’d like to know if we can do that instead. Thanks!

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