HVAC money is lumpy: five-figure install jobs one week, $200 service calls the next, and two shoulder seasons where the phone goes quiet. Books that just list income and expenses can't tell you which side of the business actually makes money. Here's the setup that can.
Split installs from service in the chart of accounts
Keep at least two income accounts — installations and service/repair — and, if you sell them, a third for maintenance agreements. The margins are completely different: installs carry heavy equipment cost and payroll hours, while service calls are mostly labor at a better margin. One lump 'Sales' account hides whether your install pricing is actually working.
Mirror the split on the cost side: equipment purchases for jobs belong in cost of goods sold, not in the same expense account as the office internet. When equipment for a job is bought in March and the job finishes in April, recording the cost against the job's month keeps each month's margin honest.
Job costing without drowning in it
Full per-job costing is overkill for many shops, but every install over a few thousand dollars should carry its own tag: equipment, materials, subcontract work, and labor hours against the invoice total. Half a dozen tagged installs a month is enough to see whether your bid margin survives contact with reality.
Progress payments and deposits on installs are liabilities until the work happens — booking a 50% deposit as income inflates this month and starves the month you actually do the work.
Maintenance agreements and deferred revenue
Annual maintenance agreements paid up front are the classic HVAC bookkeeping trap. A $300 agreement collected in April is not April income; it's earned across the visits you owe. Spreading it keeps spring from looking artificially rich and fall from looking broke, which matters when the slow months are exactly when you need to trust your numbers.
Keeping the books current year-round
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