You can add account credits to a customer's profile. The customer will be able to use account credit on any future purchases. The credit can be used in full, or can be split to use across multiple purchases.
If the customer owns a recurring membership, the account credit will be used against the next bill/s automatically.
Navigate your way to the profile page of the customer you would like to add credit to.
Click on the payments tab, and then click 'Add' next to Account Credits:
Now add a memo for the credit, and then the credit amount.
Click save once you're done here.
For this example, the customer now has £20 account credit to use on future purchase/s.