It is a good idea to establish expectations for both billing and payment in your software consulting contract. Some of these matters may include:

• Will purchase orders be issued or required?
• How often will bills be issued?
• In what format will invoices be sent? (digital via email, hardcopy via post)
• Where will invoices be sent?
• How soon must they be paid?
• What forms of payment are acceptable?
• Are there any discounts for prompt payment?
• Are there any penalties for late payment?