This is a test of commonsense. Complete the next sentence:

How to set up a billing system
Use an offline billing system.
Odds are, you are already using some type of billing system. You may keep track of payments through a written list, a stack of invoice copies, or through a spreadsheet program like excel.
If you're organized enough, this type of system can work for a small business, especially if you are handling a relatively low volume of transactions. If you don't have any type of existing billing system, consider using this type of simple, offline system before investing in billing software.