You can add a store credit to a customers account via the Admin –> Sales –> Customers menu

1. Go to Admin –> Sales –> Customers
2. Select the customer you wish to add a credit for and click “Edit” in the right side column
3. Go to the Transactions Tab
4. Type in a description and the amount of the credit in the fields then select “Add Transaction”

If you need to reverse a credit, simply create a new transaction (as per above steps) but add in a negative balance (ie -10) This will reduce the store credit they have available