Give customer a Credit

Hello, we are trying to figure out how to give a customer a credit.

We have a customer who logged in using their account.
They ordered a couple of products in the one order.
They then paid for it by credit card.

One of the products could not be supplied so we would like to apply a credit to their user login so that the next purchase they make automatically deducts the credit amount.

Is this possible? How can we do it?
Thanks
Alan

Hello Alan,
A solution can be to give them a coupon code of the value of the products that can't be supplied.

Thanks, works perfectly.