Negative values in SINV - acceptable practice?

more an accounting then ERPNExt question …

scenario is a Sales Invoice issued to a customer to whom one has to reimburse a small amount (smaller then the value of the invoice).

Let’s say the value of the goods sold is 100.- and I want to reimburse 5.- to the Customer (not a discount on those items) just an express fee that was collect from the Customer for the previous delivery which should have been paid by us. Just wondering whether it is acceptable from an accountants perspective to issue such a reimbursement within a SINV or should one always stick to Credit Notes for everything being credited to a customer (no matter how small the value)?

As I already know that techincally ERPNext can process this, my question is more a in regards to good accounting practices

I think good accounting practice would be credit note