Why does quickbooks keep applying a payment when I copy an invoice?

Hi there, 

QuickBooks is great program for managing your payments and keeping your books organized. I'll be glad to give you a hand and steer you in the right direction.

It's vital you're able to copy an invoice without a payment being applied. That being said, I'd like to get a visual reference of what you're experiencing. Could you walk me through the steps you're following to copy an invoice. Otherwise, in order to mark an invoice as unpaid again, you'll have to delete the payment on the invoice. To do this, open the invoice in question and click on where it says "1 payment made" at the top right to see the payment. From here you can delete the payment so it's not attached to the invoice. 

There you go! You now know how to mark an invoice as unpaid again. Feel free to ask other questions by leaving a comment below. I'm here to assist.