We are an animal rescue.  Our veterinarian bills us weekly.  We have a grant that pays for spay/neuter of dogs, with a $75 copay.  Instead of simply deducting the $75 from the total bill, and billing me for the balance, they credit me the $75 for each downpayment, then bill me for the total bill.  This makes it complicated for me, but easier on them.

This past week, I had 2 - $75 credits.  I already had 2 credits waiting to be used.  They deducted $150 from my total payments.  After entering everything, I realized I used the wrong 2 credits.  How do I go back and undo the credits, so I can apply the correct ones.  I can't seem to find how to show where a credit was applied, after the fact.

Thanks