You can edit a payment once it has been entered into Commusoft, in order to do this, use the search bar to enter the invoice number, or search for the customer/job and click through to the invoice.
Click 'View' on the invoice.
At the bottom of the screen under 'Payment & allocation history' navigate to 'Actions' on the right and click 'View payment'.
Click 'Edit' on the right-hand side of the 'Payment details'.
Double click the value you wish to edit under the 'Amount to allocate' column, enter the new value and Save at the bottom of the page.