Hey there, @oliver11.
 
I can help you edit the paid invoice. Here's how:
- Go to the Sales tab, then click Customers.
 - Select the customer you want to run.
 - Look for the Payment, then edit the amount.
 - From the Receive Payment window, edit the Payment amount.
 - Select the Save and new drop-down arrow, then choose Save and close.
 - From the pop-up window, click Yes.
 
Also, here are some helpful articles that you can check on for future reference about receiving invoice payment in QuickBooks Online:
 
Stay posted if you have any other payments or deposits questions, I'll be always here to help you. Have a great day ahead!