For more than 30 years, we have used the SAFE system with most of our major clients. SAFE stands for "simplified accounting, fixed expense". Under this system, we neither bill for over-expended costs nor refund unexpended costs.
The assumption, which has proven accurate for as long as we have used the system, is that the two principles offset each other and, at the same time, relieve both us and our client from the unnecessary time and expense of accounting for the small aounts involved. It also has the benefit of letting the client know from the very beginning what their total financial expsoure is. Finally, since we don't have to wait for the client to front minimal additional costs, we are able to institute post-judgment remedies (such as garnishment) immediately when the opportunity presents itself.
If you want more information about the SAFE system, please contact Justin D. Jacobson.