Audit is a recurring business, and recurrence hides two problems
Predictable work is the easiest work to schedule badly
An audit practice knows most of its year in advance. The same clients need the same engagements at broadly the same times, and yet the calendar in most firms is assembled reactively, one phone call at a time. The result is a familiar shape: three assignments landing in the same fortnight, a manager carrying two engagements she cannot both be present for, and a client who assumed you had them scheduled because you audited them last year.
Creating recurring engagements ahead of time, with dates and provisional team allocation, converts that into a planning problem you can solve in a calm month. Overlaps become visible while there is still room to move a team, extend a timetable or decline an assignment that was never going to fit.