They did a good job completing my business taxes accurately. Two things bothered me: 1. they werent transparent with billing and 2. they are expensive (I found a great accountant for 30% less). As with anything in billing, the main thing is transparency. The fee structure should be spelled out clearly in the engagement letter. Whether you are paying a monthly fixed fee, annual fixed fee, or hourly rate, you should know the price tag of asking a question before you ask it.