Here's how we roll......
All customers sign a contract. They have the option of paying in full each month for services performed, or having a 12-month contract with fixed monthly payments for all subscribed services. We have a clause that if there is inclement weather or mechanical troubles, and we can't make it out in time -- we will pro-rate the invoice for that month's service. Invoices are printed/mailed the 1ST of each month and are due on the 10TH. This has proven to be a very simple and effective system.