Here is a checklist for effective invoices

Obviously, I assume that the invoice indicating the amount due, and items purchased. But this is only the beginning ...

>>> 1. The invoice shall include a specific expiration date? >> 2. The bill tell the customer exactly how to pay? >> 3. The bill includes a telephone number the customer can call if you have questions? >> 4. The bill includes payment terms? >> 5. Your invoice must include a description of the penalty for late payment?