How to handle refunds to customers？

[Ben79]

An invoice has been issued and the customer has paid in full. However, due to reasons such as price reductions, a portion of the payment needs to be refunded to the customer. I need to reduce the invoice amount and refund the excess payment to the customer. How should I handle this?

1. If I issue a Credit Note, I cannot “apply” it to an already paid invoice. Can I only modify the original invoice，like recognize a discount?

2. How do I record the payment? If I use Refund, it will be recorded as a receipt instead of a payment.