Why is the system so complicated, I just want a button to mark an invoice as paid

Hello Ncjones21@gmail.

Welcome to the Community page, 

Have you received payment on this invoice as once you have done that it will then show as the invoice has been paid off?  

So open the invoice>click receive payment> make sure details are right, click save and then ti should show that invoice as been paid off.  

Any Q's let us know