When you're faced with a long-term project with clearly defined goals, charging by the project is the way to go. Gail Gudell, an independent accountant, uses this approach. I act as Chief Financial Officer at three of my clients' companies. I developed a specific checklist of duties, forms, and reports that I'm going to provide on a weekly, monthly, quarterly, and yearly basis. And I am paid on a contract basis for performing these CFO functions.
Clients usually prefer to pay on a per-project basis.
They're scared of giving IPs free rein and getting a nasty surprise down the line. Alternatively, charging by the project works well when you're providing one specific service or product to your client. Take, for example, an illustrator who's been asked to draw a picture for a company's brochure. He should determine what the illustration's value is and charge his client that amount. A Client's Perspective Clients often prefer to pay on a per-project basis.