I've looked through a few different EDI 820 specs online and have not seen any guidance as to how to handle the monetary amount (BPR.02) when the Credit/Debit Flag Code (BPR.03) is "D". If the code is D, should the amount be negative or positive? Is the amount allowed to be negative at all, per the spec?
I searched through my company's internal EDI spec, as well as a few online versions. None mentioned how to handle the amount when the Credit/Debit Flag Code is D, and none that I looked at even showed an example of a transaction in which BPR.03 was "D".
X12 usually specifies or explains when a number can be negative in the syntax notes. For example, let's look at the ADX (Adjustment) segment (https://www.stedi.com/edi/x12-008010/segment/ADX).
ADX01 specifies the amount of the adjustment and must be signed if negative. If negative, it reduces the payment amount; if positive, it increases the payment amount.
However, it looks like the BPR segment (https://www.stedi.com/edi/x12/segment/BPR) doesn't have any syntax notes for the 02 / 03 elements.
I'd expect the number to be positive following the debit or credit qualifier code in the BPR-03.
Credit = payment
Debit = refund
Technically, a negative debit could be a credit, but I don't see the benefit of expressing it that way given the presence of the flag.