atx organizer has an engagement letter that i modify each year, but its a good starting point and doing it through atx makes it automatic. Mine is about 3 pages long and discusses fees, how and when i get info, their responsibilty for keeping records, fees, penalties if they want estimated vouchers for any amount not 100/110 of current year, etc. The few questions i got when i started i just answered with, its required and we need it for our files., never had an objection either.