I'm here to help you enter a payment even without an invoice in QuickBooks Desktop.
QuickBooks Online has the flexibility to enter a payment without an invoice. You will first need to create a credit memo and then apply it to the invoice later on.
Here’s how to create a credit memo:
These articles are a good reference:
Drop a reply below if you need more help about invoices and payments in QuickBooks Online. Have a great rest of your day.