::Hi Calvin:
There are a few ways and a few places – including an automated write off where you code in the limit you are willing to write off and all short-paid invoices or over-paid invoices will write off that small amount.
First, in Sales Apply Document – a window used during cash receipts and applying payments and credit memos. as in the first screenshot here: (Caveat: If your company is setup to not allow write offs or limits you might not be able to do this)
The same functionality is in Purchasing.
In sales there is also the “Write Off” routine