Cash receipts

Hello experts,

I have to pay several invoices for a customer. The invoices are made with 30 days bank transfer payment term. I have a sales person who colletcts the money from customers, and comes in, and pays the invoices in cash and i have to give him a document that proves he paid the invoices. I have Cash receipt available in Financial modul. I want to pay several invoices but when i try to post the cash receipt, NAV returns the following message:

“Only one line with Account type Customer or Vendor is allowed”

If i do it one by one it works. Can you please tell me what is the problem, and how to solve it?

Thanks,

Otto