The 13-week
cash flow forecast.

The short answer

A 13-week cash flow forecast is a simple grid: one column per week for the next quarter, cash coming in on top, cash going out below, and the projected bank balance at the bottom of each column. That bottom row is the whole point — it shows you the low-water marks weeks before you hit them.

Why 13 weeks? It's a full quarter — far enough out to see a crunch while you can still do something about it (accelerate a draw, slow a payment, tap the line), near enough that the numbers stay real instead of hopeful. And why weekly? Because contractors don't run out of cash on average — they run out on a specific Friday. A monthly view shows a fine month; the weekly view shows the payroll on the 12th landing before the draw on the 25th.

Why contractors specifically need one

Construction cash flow is lumpy in both directions: big draws in, big sub payments out, payroll every week no matter what, and retainage trickling in months behind the work. A "profitable" quarter can contain two weeks of genuine crisis — we covered the mechanics in Why Profitable Contractors Run Out of Cash. The 13-week forecast is the operating tool that catches those weeks in advance. Your P&L measures whether you're winning; this measures whether you'll make payroll while you win.

What goes in it

Cash in — by source, by realistic date

• Pay app collections — draws already submitted, timed by when each customer actually pays, not the contract's 30 days. Your AR history knows the truth.
• Draws not yet submitted — from each job's billing schedule.
• Retainage releases — their own line, tied to realistic closeout dates.
• Everything else — deposits on new work, refunds, planned line-of-credit borrowings shown as what they are.

Cash out — the honest list

• Payroll and payroll taxes — every week or two, immovable, first on the list.
• Subs and suppliers — from AP due dates and known commitments, including pay-when-paid timing.
• The fixed nut — rent, insurance, loan payments, software, fuel.
• The lumpy ones people forget — quarterly taxes, insurance audit true-ups, equipment purchases, owner distributions.

What it looks like

Weeks 4–6 are the story: a hole that exists today, visible a month early — while there's still time to pull a draw forward, stage sub payments, or draw the line.

Seen in week one, that hole is a planning problem with half a dozen solutions. Discovered in week four, it's a crisis with two — and both are expensive.

How to keep it honest

1. Update it weekly. Thirty minutes, every Monday: replace last week's guesses with what actually happened, roll a new week 13 on. A stale forecast is worse than none — it's confidence without accuracy.
2. Use real payment behavior. The customer who pays in 45 days goes in at 45 days, whatever the contract says.
3. Keep a "week 13 rule" for wishful thinking. Unsigned work and hoped-for change orders don't enter the forecast until they're real. The forecast is for cash you can defend, not cash you can imagine.
4. Track forecast vs. actual. If week-one projections keep missing by 20%, the input assumptions need fixing — that feedback loop is what makes the tool sharp.
5. Build it on reconciled books. The forecast starts from your AR, AP, and cash balances. If those are wrong, every column inherits the error.