A seller handed me three years of annual P&Ls showing steady 10% growth. Looked clean. Then I pulled the monthly statements and found July was carrying the entire year — eleven months were flat or declining. The “growing” business was actually a one-month wonder with a fading customer base. I walked. The next buyer didn’t ask for monthlies. He closed. He called me fourteen months later asking if I knew anyone who wanted to buy an HVAC company.
Every due diligence checklist tells you to request “trailing 2–3 years of financial statements.” Most buyers take that to mean annual summaries. The seller’s CPA sends over three tidy P&Ls, one per year, and the buyer stares at the revenue line, the expense line, and the SDE number at the bottom.
That is not enough. Not even close. Not for HVAC.
HVAC revenue swings 300–500% between peak and trough months. A company doing $1.8 million a year might do $280,000 in July and $47,000 in November. The annual summary averages all of that into a single number that tells you almost nothing about how the business actually operates — or whether the numbers are real.
You need 36 consecutive months of P&L statements. Monthly. No exceptions. Here is what they reveal and how to read them.
Why Monthly Matters More in HVAC Than Almost Any Other Trade
Plumbers get steady calls year-round. Electricians are project-driven but not seasonal. HVAC has a dual-peak revenue cycle that creates two cash generation windows and two cash burn periods every single year.
The dual-peak pattern:
- Cooling season (June through August): The first and usually larger revenue spike. Emergency AC calls, system replacements, and new installs.
- Heating season (November through February): The second spike. Furnace failures, heat pump issues, boiler work.
- Shoulder seasons (March through May, September through October): Revenue drops 40–70%. You are running maintenance agreements and hoping the phone rings.
The depth of each peak, the severity of each trough, and the ratio between them varies by geography, service mix, and customer base. A company in Phoenix has a monster cooling peak and a modest heating bump. A company in Minneapolis is the reverse. A company split 50/50 residential and commercial has a flatter curve than a pure residential shop.
The annual P&L hides all of this. Monthly data shows you the actual shape of the business.
The Five Things Monthly P&Ls Expose
1. Revenue Timing Manipulation
This is the most common seller trick in HVAC deals, and the annual P&L cannot catch it.
Here is how it works. The seller knows he is going to market the business in Q1. So in December, instead of invoicing the last two weeks of work, he pushes those invoices to January. Revenue that belongs in Year 2 shows up in Year 3 instead, making the trailing year look stronger.
Another version: pulling prepaid maintenance agreements forward. A customer pays $480 for a two-visit annual agreement in November. The seller books it all in November instead of recognizing $240 in November and $240 in May. The last year’s P&L inflates by $240 per agreement, times a hundred agreements.
How to spot it in monthlies:
- December revenue that drops off a cliff compared to the prior two Decembers
- January revenue that spikes 30–40% above the prior two Januaries
- Maintenance revenue that bunches in one month instead of spreading across the contract term
Compare December-to-January transitions across all three years. If Year 3 looks different from Years 1 and 2, ask why. The seller will have an explanation. Sometimes the explanation is weather. Sometimes it is fraud.
2. Actual Seasonal Cash Flow Patterns
This is about survival, not valuation.
When you buy an HVAC business, you are buying into its cash cycle. If you close in September, you have about six weeks of shoulder season before heating calls start. If you close in March, you have two months of dead air before cooling season saves you.
Monthly P&Ls show you:
- How deep the troughs actually go. An annual P&L showing $1.8M in revenue and $200K in SDE does not tell you that January through March the business burns $12,000–$18,000 a month in negative cash flow.
- How many months the business runs negative. Some shops have two bad months. Some have five. The difference is the difference between a $50,000 line of credit and a $120,000 one.
- Whether the shoulder seasons are getting deeper. If March and April revenue dropped 15% each year for three years, the seasonal trough is widening. Your off-season cash management plan needs to account for the trend, not the average.
3. Year-over-Year Trajectory by Month
“10% annual revenue growth” is the most misleading number in small business sales.
Pull the monthly data and compare each month to the same month in the prior year. January Year 3 versus January Year 2. February Year 3 versus February Year 2. All twelve months, all three years.
What you are looking for:
- Broad-based growth means most months grew 8–12%. That is a healthy business with organic momentum.
- Spike-driven growth means one or two months had a monster year (a large commercial project, a heat wave, a furnace recall) and everything else was flat or down. The “growth” is an event, not a trend.
- Decelerating growth means Year 1 to Year 2 grew 15%, Year 2 to Year 3 grew 5%. The seller is listing at peak.
- Masked decline means the annual number looks flat, but six months are declining 10% while two months are up 30%. The business is concentrating — losing diversity, gaining dependence on fewer large months. That is fragile.
If you are building a pro forma revenue model, month-level trajectory is the only honest foundation. Annual trend lines lie.
4. Expense Timing Anomalies
This is where sellers inflate SDE in the trailing twelve months before a sale.
Common moves:
- Deferred vehicle purchases. The fleet needed two new vans in Year 3 and the seller held off. Monthly vehicle maintenance expense spikes 40% in the last six months because he is keeping dying trucks alive instead of replacing them. You are buying deferred capex.
- Marketing cuts. The seller stopped running Google LSAs or Yelp ads six months before listing. Monthly marketing spend drops from $4,500 to $800. Revenue has not caught up yet — but it will, and you will be the one watching the phone go quiet. (See the lead generation migration risk guide for more on why this matters.)
- Delayed hires. A tech left in Month 18 and was never replaced. The remaining techs absorbed the load, overtime spiked, and the payroll line looks artificially lean. You are buying a shop that is one quit away from a scheduling crisis.
- Insurance timing. Workers’ comp and liability premiums are annual. If the renewal happened to fall early in Year 3, it front-loads expense and makes the trailing twelve months look worse than ongoing run-rate. If it fell at the end, the trailing twelve months look better.
How to read it: Line up each major expense category month by month. Circle anything in the trailing 12 months that breaks pattern from Months 1–24. That is your list of “why did this change” questions for the seller.
5. Revenue vs. Cash Collection Lag
If the business does any commercial work with 30–60 day payment terms, the monthly P&L shows revenue the business has not actually collected yet.
Annual statements mask this completely. Monthly ones show you:
- Months where receivables spike. September might show $180,000 in revenue but only $110,000 in collections because commercial customers pay Net 45.
- Collection cycle lengthening. If the gap between revenue booked and cash received grows across 36 months, customers are paying slower. That is a working capital problem you are inheriting.
- Seasonal collection mismatches. Commercial HVAC often books big install revenue in summer but collects in fall. If you close your deal in August, you are taking over $200,000 in receivables that the seller booked as revenue but you have to actually collect.
Run the monthlies alongside 36 months of bank statements. If revenue and deposits do not reconcile within 45 days, you have a receivables problem worth digging into.
How to Request and Analyze 36 Months of Monthly P&Ls
Step 1: Make the Request Early and Specific
Put it in your LOI or your initial document request list. Do not wait until deep diligence.
The exact ask: “Monthly profit and loss statements for the trailing 36 months, generated from QuickBooks (or whatever accounting software is used), in the same chart of accounts format, with no manual adjustments.”
The “no manual adjustments” part matters. You want the raw output, not a version the seller’s CPA cleaned up. Cleaned-up versions reclassify expenses to make SDE look better.
If the seller pushes back and says he only has annual statements, that tells you something important: either the bookkeeping is a mess, or the seller does not want you to see the monthly data. Neither is good.
Step 2: Build a 36-Month Spreadsheet
Create a single spreadsheet with 36 columns (one per month) and every P&L line item as a row.
Revenue rows:
- Residential service/repair
- Residential install/replacement
- Commercial service/repair
- Commercial install/project
- Maintenance agreements
- Other (duct cleaning, IAQ, etc.)
Expense rows:
- Payroll (techs, office, owner)
- Vehicle costs (fuel, maintenance, payments)
- Parts and materials
- Marketing and advertising
- Insurance (liability, workers’ comp, vehicle)
- Rent and facilities
- Software and tools
- Everything else
Step 3: Run the Comparisons
With 36 months laid out, run these five analyses:
- Same-month year-over-year. Each month compared to the same month in prior years. Flag any month that moves more than 20% in either direction.
- Trailing 12 vs. prior 12. Sum the most recent 12 months and compare to the 12 before that, line by line. This is your real growth rate.
- Peak-to-trough ratio. Best month divided by worst month, each year. If the ratio is widening, the business is getting more seasonal and harder to finance through the troughs.
- Expense trend breaks. Any expense line where the last 12 months break pattern from the first 24. Circle it. Ask about it.
- Revenue mix shift. If commercial revenue went from 40% to 25% of the total, the business lost its commercial base. If maintenance agreements went from 20% to 8%, the recurring revenue is evaporating.
Step 4: Cross-Reference Against Bank Statements and Tax Returns
Monthly P&Ls are only as honest as the person who entered the data. Cross-reference:
- Monthly bank deposits against monthly booked revenue. According to the QuickBooks forensics guide, gaps here are the single most common indicator of unreported income or fabricated revenue.
- Annual tax returns against the 12-month P&L total. If the P&L shows $1.8M and the tax return shows $1.5M, someone is lying to either you or the IRS. Both are problems.
- Payroll tax filings (941s) against monthly payroll expense. The IRS gets quarterly payroll reports. These are very hard to fake. If the 941 shows $28,000 in quarterly wages and the P&L shows $42,000, those phantom employees are either owner add-backs the seller forgot to mention or expenses that do not exist.
Step 5: Build Your Real SDE From Monthly Data
Once you have clean monthly data, rebuild SDE from scratch.
Do not trust the seller’s SDE number. Take the 36 months, identify the add-backs you can actually verify, strip the ones you cannot, and compute your own trailing-twelve SDE.
Then compute it for each twelve-month window: Months 1–12, Months 7–18, Months 13–24, Months 19–30, Months 25–36. If SDE is climbing, you have a real trend. If it spikes only in the most recent window, the seller optimized for the sale. Your valuation math should use the middle window, not the best one.
The Red Flag Checklist: Patterns That Should Kill the Deal
Print this. Tape it to your desk. If your 36-month analysis shows any of these, either renegotiate the price dramatically or walk.
- December-to-January revenue shift in the trailing year only. Revenue pushed forward to inflate the sale year. The SDE number is fake.
- Marketing spend drops more than 50% in the last 12 months. The seller is harvesting the pipeline you will not have. Revenue decline is coming — you just cannot see it yet.
- Monthly payroll drops while revenue stays flat. Either the owner is doing the work of a tech he did not replace (and you are paying a premium for his sweat equity), or he is using 1099 contractors in ways that will not survive an IRS audit.
- Three or more months of negative cash flow each year with a deepening trend. If the trough is getting worse, your working capital needs are higher than the seller’s were. Price accordingly.
- Revenue concentration: one or two months contribute more than 40% of annual revenue. One bad summer or one mild winter wipes out the year. That is not a business — it is a bet on weather.
- Maintenance agreement revenue declining. Service agreements are the bedrock of HVAC business recurring revenue and valuation. If they are shrinking, customers are leaving and the seller is not replacing them. The customer base is eroding under the surface.
- Commercial receivables aging past 60 days and growing. The business is funding its customers’ cash flow. You will inherit that float and need working capital to cover it.
- Vehicle maintenance costs spiking in the last 12 months. The fleet needed replacement and the seller deferred it. You are buying $80,000–$120,000 in truck replacements the P&L does not show.
- Owner payroll drops in the trailing year. The owner cut his own salary to inflate SDE. Classic move. Compare owner comp across all three years.
- Insurance premiums flat while revenue grows 20%. Either the seller under-reported payroll to his workers’ comp carrier (your liability), or the policies are inadequate for the current scale. Both cost you money after closing.
The Bottom Line
Annual P&Ls are marketing documents. Monthly P&Ls are operating documents. One tells you the story the seller wants you to hear. The other tells you the story the business actually lived.
Requesting 36 months of monthly data is not aggressive. It is not unusual. Any seller with clean books can produce it in twenty minutes from QuickBooks. If a seller cannot — or will not — that is the biggest red flag of all.
You are about to sign a personal guarantee on a seven-figure SBA loan. You are going to pledge your house. The least you can do is look at the actual numbers before you sign.
Every month. All 36 of them.