Thanks for hopping in this thread, @513051895066208. Let me add more information to clarify things about customer's overpayment. 

You don't need to create a Credit Memo for this as it is already an AR credit and will be available when you create the next invoice for the customer. Thus, creating a credit memo will only generate a duplicate entry for the same value. 

This will also show in the summary of your customer's statement of accounts. Then, you can choose how you want to handle the available credit on your next transaction with the customer. 

For future reference, read through this article: Transfer customer credit from one job to another. It helps you learn about how you can assign credit from one customer to another. 

Feel free to message again should you have more concerns about anything else. We're always delighted to assist. 

Mark the post that answers your question by clicking on "Accept as solution".