Final answer:
Hourly billing is considered the most complicated method for calculating legal fees due to the meticulous documentation required for each task the lawyer performs and the need to multiply the hours by the lawyer's rate.
Step-by-step explanation:
The most complicated method for determining and calculating legal fees is typically considered to be hourly billing. Unlike a flat fee, where a lawyer charges a set amount for a service, or a contingency fee, where the lawyer is paid a percentage of the money recovered in a case, hourly billing involves detailed tracking of the time a lawyer spends on a client's matter. Each task is recorded, and the lawyer charges their hourly rate for the actual time spent. The complexity arises from the need to meticulously document each task and the duration it takes and to provide a detailed invoice to the client. A retainer fee might initially seem complex, as it's an upfront fee that can be applied to hourly billing or other fee structures, but it's essentially a prepayment for future services and does not inherently complicate the calculation of the fees.