credit notes applying multiple times to different invoices

[CStewart]

I have been using quickbooks since day one and currently run several separate companies on QBPro & am having an issue with only one of them.

We first discovered last fall that the customer centre, aged summary & a/r statement (for one customer) all had different balances.
Hours later, I figured out that a single credit note for $28.65 had been applied in full on 3 different dates to 3 different invoices.
At the time, I had just let someone go who didn't know as much as she thought she did & wouldn't listen to instructions. She was involved with all three of the above transactions & I assumed she had figured out how to do this. I managed to fix it and thought all was well.

Until today.
My assistant brings me the same problem - now with 4 customers, one of which is the same credit note & same customer as above.
Now, the credits in question have been applied 5 or 6 times all on different dates and all to different invoices.

Has this ever happened to anyone else?
Does anyone have a suggestion of how to fix it?
Or stop it from happening again

[Joe Williams]

I am not sure what your assistant is doing. The credit from a Credit Memo should show as credit to be applied on the Receive Payment for the selected invoices. They should just select the invoice to apply it to and should not spread it to all of the open invoices.
Try and get them to explain Step By Step of how they apply the credit.