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13-week cash flow forecast

Profit and cash are different things, and the gap between them is where contractors get caught. Thirteen weeks is the horizon far enough out to act on and close enough to be worth trusting.

Method reviewed by Darren Lim, US CPALicence CPA.74253602

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Spread across the next eight weeks in this model.

How you actually get paid

Off your own ageing report. The pattern in your head is faster than the real one.

Money going out

Materials, field payroll, subs.

Include it. Pretending otherwise makes the forecast useless in the week it matters.

Tax payment, insurance renewal, a truck deposit.

Your numbers

Lowest point

$27,200

Cash never goes negative in the next thirteen weeks. The tightest week is week 4 at $27,200.

Collection pattern totals5.0% of invoicing is never collected in this model — check that is what you meant95.0%
Out per week$22,200
Closing cash, week 13$71,700

Week by week

Week 1$38,300
Week 2$34,600
Week 3$30,900
Week 4$27,200
Week 5$37,800
Week 6$48,400
Week 7$59,000
Week 8$69,600
Week 9$69,500
Week 10$69,400
Week 11$69,300
Week 12$69,200
Week 13$71,700

A simplified model — invoices are assumed to land in the week their collection bucket matures. It is built to show you the shape and the week it turns, not to predict a balance to the dollar.

Why thirteen weeks

A quarter is long enough that a problem is still fixable when you see it — you can chase receivables, delay a purchase, or call the bank while you still have options. It is short enough that the numbers are real rather than a budget you invented in January.

Beyond thirteen weeks the assumptions stop being knowledge and start being hope. Inside it you are mostly working from invoices that already exist and bills that have already arrived, which is the difference between a forecast and a wish.

Collections, not sales

The single biggest error in cash forecasting is putting revenue in the week the work was done. Cash arrives when the customer pays, which for most contractors is thirty to sixty days later and sometimes considerably longer.

So the forecast runs on your collection pattern: what share of an invoice lands within thirty days, what share by sixty, what by ninety, and what never arrives at all. Take those percentages off your own ageing rather than off an assumption, because the assumption is always optimistic.

The same discipline applies going out. A bill received is not cash gone; cash goes when you pay it, and your own terms are a lever most contractors forget they are holding.

What to do with the week that goes red

A forecast that shows a shortfall in week nine is not bad news. It is nine weeks of warning, which is enough to fix it with a phone call rather than a loan.

In order: collect what is already overdue, invoice anything completed and unbilled, ask suppliers for terms before the invoice is late rather than after, and draw on a facility you arranged when you did not need it. Every one of those is easier at week one than at week nine.

Run it again every Monday. The value is not the forecast — it is noticing the shape changing.

Common questions

What collection percentages should I use?
Your own, from your own aged receivables report. Total what was collected within 30, 60 and 90 days over the last few months and convert to percentages. Almost every contractor who does this for the first time finds their real pattern is slower than the one they had in their head.
Should I include the owner draw?
Yes. It is cash leaving the account and pretending otherwise makes the forecast useless in exactly the week it matters. If your draw is variable, put in the minimum you actually need to live on.
Does this replace a budget?
No, and they answer different questions. A budget is about whether the year works. A cash forecast is about whether Friday works. Profitable businesses run out of cash regularly and it is almost always the second question that catches them.

What we do about it

An aged receivables report and a forward view of committed costs arrive with your monthly pack, so the inputs to this are current figures rather than estimates you assembled from memory.

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