HVAC bookkeeping.
Know which calls actually make money.

HVAC businesses run three fundamentally different jobs under one roof, and most bookkeeping treats them as a single revenue line. An install is equipment-heavy and labor-light relative to its price. A service call is the opposite — mostly labor and drive time against a small parts ticket. A maintenance agreement is neither: it's revenue you collected months ago against a visit you're performing today. Blend all three into one monthly number and you can't tell which one is actually funding the other two.

The next failure is COGS versus overhead. A condenser, a compressor, a case of refrigerant — those are cost of goods sold, tied to a specific job. A truck payment, a shop lease, the office manager's salary — those are overhead, and they belong to the business, not to any one ticket. When both get dumped into "job costs" without distinction, gross margin stops meaning anything, because it moves with how many trucks you leased this month rather than how the jobs actually performed.

Technician pay compounds it. Spiffs for upselling a maintenance plan, commission on install sales, overtime during a July heat wave — all real costs of doing that specific job, and almost never coded back to it. A technician can look expensive on payroll and be the most profitable person in the company once you see what they actually closed.

Then the season itself. July and January carry the year; April and October barely cover payroll. Cash planning built on a flat monthly average rather than the actual seasonal curve is what turns a normal slow month into a payroll scramble.