Closing an open invoice that shows a balance due

[mbanas]

I am using version 11.5 and I have an open invoice where a customer paid $100 toward a $300 retreat. Now she will not be attending the retreat. She does not want a refund, she wants her payment of $100 to be a contribution. How do I close out her open invoice (which shows a balance due) and make that payment a contribution?
Any help is appreciated,
mbanas

[Matt]

Create a payment for that invoice, but input it as a negative $100. Then post the negative payment. This will "undo" the original posting. You'll then need to reduce the $300 invoice to $0 and then post in Accounts Receivable to archive it.

Then, enter the $100 in the Contributions Module as a contribution and post to both the Contributions Module and Fund Accounting.