Your year is one long quiet stretch and one impossible month
Capacity problems are created months before they appear
Tax preparation has a demand curve unlike almost any other service business. For much of the year the office is manageable. Then a short window arrives in which every client wants attention simultaneously, everyone in the office works late, and the quality of the experience a client gets depends mostly on when they happened to walk in.
Almost none of that crunch is inevitable. It is the compound result of decisions made earlier: not contacting last year's clients until they contacted you, not requesting documents until the client asked what you needed, and not knowing which preparer was filling up until they were full. Those are scheduling problems.