Some legal work is done on a fixed fee basis.
This tends to be in straightforward cases, where it is not hard to predict how much time will be spent to finish the job. So they must have financial income targets, maybe weekly or monthly, which have to be met to pay the expenses. Anything left after paying expenses, and V.A.T. on the costs, is profit before tax. Because of this, work is usually charged at an hourly rate, and even in fixed fee work the business needs to know how much in costs per hour the work is likely to bring in. Hours are usually split into 10 units, for convenience.