Cash Flow for Service Businesses
Profitable service businesses go broke every day. Profit is an opinion; cash is a fact. This guide is the full playbook on the 13-week forecast, seasonal traps, lines of credit, and the seven numbers every owner should check weekly.
$1.6M
cash difference between 30-day and 90-day DSO at $10M revenue
13 weeks
the right horizon for a rolling cash forecast
40%
of revenue in busy months, for many seasonal contractors — the trap
Why profitable service businesses go broke
Profit is an opinion. Cash is a fact. A contractor can post a $500K profit on the P&L and still bounce payroll, because profit is recognized when work is done and cash arrives 30–90 days later — sometimes never.
The classic failure mode is growth-driven bankruptcy. Revenue is up 40%, the team grew, the trucks expanded — and the business runs out of cash three months in because every new job consumed working capital before the old jobs got collected. The bigger the company gets, the bigger the cash hole.
Cash flow management is what separates contractors who scale from contractors who blow up trying to.
The takeaway: If you can grow yourself out of business, you have a cash flow problem, not a revenue problem.
The 13-week cash forecast
The single most important cash management tool a service business can build is a 13-week rolling cash forecast. It's not budget. It's not P&L. It's a week-by-week projection of inflows (collections from existing AR plus new invoicing) and outflows (payroll, AP, debt service, taxes), with a running cash balance.
13 weeks is the right horizon because it covers a full quarterly tax cycle, captures most of your AR aging curve, and gives you enough lead time to take action — collect harder, delay AP, draw on a line of credit, or pull back on hiring — before a problem becomes a crisis.
Most contractors don't have one. The ones who do almost never run out of cash unexpectedly. The forecast is the early warning system.
The seasonal trap
HVAC, landscaping, roofing, restaurants — most service businesses have material seasonality. The trap is that owners forecast cash off the busy months and build a cost structure that doesn't survive the slow ones.
An HVAC contractor doing 40% of revenue in July through September has to fund the full year's overhead from a 3-month cash window. If the seasonal cash-out covers payroll for the next 9 months and the owner's distributions, fine. If it covers 6 months and a new truck, you've just guaranteed a Q1 cash crisis.
The fix is to build the trough into the forecast. Plan for the slow quarter as if it has no revenue at all. If the business survives that scenario on cash reserves and seasonal AR collection, you're solvent. If it doesn't, you're managing a structural cash flow problem, not a temporary slowdown.
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The 7 numbers every owner should check weekly
- Cash on hand. Bank balance, every Monday morning. Track the trend, not the snapshot.
- AR aging buckets. 0–30, 31–60, 61–90, 90+. Anything over 60 days needs a name and an action.
- AP aging. What's owed and when. AP is your free working capital — but only if you don't blow up vendor relationships managing it.
- Backlog. Booked work not yet performed. This is your near-term revenue visibility.
- Pipeline conversion. Quotes outstanding, win rate, average deal size. Lagging signal of pricing health.
- Job-level margin on completed jobs. Last week's actuals. Trend matters more than the snapshot.
- Burdened labor cost as % of revenue. The single best leading indicator of margin compression.
Debt, lines of credit, and the cost of waiting
A line of credit isn't a sign of weakness. It's the cheapest insurance against a 60-day AR delay. The contractors who don't have one are the ones who get blindsided when a big customer slow-pays.
The right time to get a line of credit is when you don't need it. Lenders price risk on cash flow stability and balance sheet health — both of which are at their best when you're not in trouble. If you wait until you need the line, you're borrowing at distressed rates from people who know it.
On the other side: debt becomes dangerous when it stops being a working-capital tool and starts funding operating losses. If your line is rolled over month after month at the max, you don't have a financing problem — you have a profitability problem hiding behind one.
Why field software alone won't fix this
ServiceTitan, BuildOps, Jobber, Housecall Pro — these are excellent operational tools. They run dispatch, scheduling, invoicing, and customer comms beautifully. They are not cash flow management tools.
Field software is built around the job lifecycle. Cash flow is built around the AR-to-AP cycle, payroll timing, tax obligations, and capital structure. The two systems intersect (your invoices come from FSM) but they're not the same thing.
The contractors who get this right have field software for ops, accounting software (QBO, Sage, Spectrum) for the books, and a cash flow forecast that pulls from both. The ones who get it wrong assume their FSM dashboard is telling them about cash. It isn't.
Use the data yourself
Frequently asked
How much cash on hand should a service business have?
The standard answer is 3 months of operating expenses. For a seasonal service business, the better answer is enough cash to fund operations through the slowest 90 days of the year plus a 30-day buffer. For a $10M HVAC contractor with $300K monthly opex, that's $1M+ of operating cash. Less than that and any AR delay or seasonal slowdown becomes a payroll crisis.
Should we open a line of credit?
Yes, almost always. The line is insurance, not debt. The right size is roughly 60–90 days of operating expenses, secured against AR or business assets. Banks will offer it when your financials are clean and your relationship is healthy — meaning the time to apply is when you don't need it. The cost of having an undrawn line is low (a small commitment fee). The cost of not having one when you need it is high (vendor terms collapse, distressed financing, missed payroll).
What's the right cadence for cash flow forecasting?
13-week rolling forecast updated weekly. Every Monday: roll forward one week, true up the prior week's actuals, refresh AR collections projections, refresh AP payment plan, run the new ending balance. The forecast is only as good as the discipline of updating it. A 13-week forecast updated quarterly is worse than no forecast — it gives owners false confidence in numbers that are already stale.
How do you forecast cash collections from AR?
Bucket your AR aging into 0–30, 31–60, 61–90, 90+. Apply historical collection rates by bucket: typically 80–95% on 0–30 day AR collected within the next 30 days, 50–70% on 31–60 day AR, 25–50% on 61–90 day AR, and 5–25% on 90+ day AR. Layer in known events (large invoice expected, customer dispute pending) on top. Re-run weekly. After 8–12 weeks of doing this, your forecasts will be within 10% of actuals.