How do you handle Bank charges

How do you handle Bank charges

Say i bill a client $500. He pays the bill via paypal who charge say $50 and I get a net $450. I transfer that from Paypal to my business account. The bank feed comes in as 450 and the invoice is for 500. 

When I try to close the invoice by recording payment it has a place for bank charges but when I enter a no in that and try saving it I keep on getting a message 'Select account to deposit Bank charges".. Not sure what the answer is for that. would appreciate your help. thanks in advance..