We have clients who pay in cash and often will round up, or they pay more than one invoice at a time with a single payment. Not allowing a credit option automatically and not allowing us to apply a single payment to multiple invoices means we have to take multiple steps and the record does not accurately reflect what happened. If a client has 2 open invoices, one for $500 and one for $475, and they pay $1,000 at one time and know they'll have more invoices, it makes sense for us to enter that as 1 payment, apply it to 2 invoices, and have a $25 credit.