" If the same check number was used to pay for two separate orders, would you have entered 123a and 123b for the check numbers in OE, since the duplication was not an entry error but in fact the 'desired method of entry'?"

That's what I ended up doing to fix the error batch in AR. In this case I was the culprit, so when the errors occurred in AR I new what was happening and it was a quick fix (assign new cheque number 123a). But there could be cases where one person does the entry in OE and someone else posts the batch in AR. Then the AR person must back track and make sure that it wasn't a data entry error - time consuming. I'll let everyone in the office know but chances are it will be forgotten in a few days. A warning in OE would be nice but I know that's not likely to happen since the payment option is there as a convenience.

Thanks