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Cash Flow••6 min read

How to Build a 13-Week Cash Flow Forecast (Contractor Edition)

You can't manage cash by checking your bank balance. Here's the rolling 13-week forecast that keeps contractors out of trouble.

Cory Salisbury
Cory Salisbury
Founder & Fractional CFO • Salisbury Bookkeeping

Why 13 weeks?

13 weeks = one quarter. That's far enough out to see payroll crunches, draw gaps, and material bills before they hit. It's close enough that the numbers are still reliable.

Checking your bank balance is not cash flow management. It's rearview driving. The 13-week forecast puts headlights on.

The structure

Your forecast has 5 rows. That's it.

  1. Starting cash. What's in the bank on Monday morning.
  2. Cash in. Customer payments, draws, retainage collections, deposits.
  3. Cash out. Payroll, subs, materials, equipment, overhead, loan payments.
  4. Net cash flow. Cash in minus cash out for the week.
  5. Ending cash. Starting cash plus net cash flow. This becomes next week's starting cash.

Roll it forward every Monday. Drop the oldest week, add a new one at the end.

Where contractors get it wrong

Mistake 1: Counting revenue, not cash

An invoice is not cash. A draw request is not cash. Only count money when it hits the bank. Use your actual payment history to estimate timing — most GC payments take 30–45 days.

Mistake 2: Forgetting lumpy expenses

Quarterly insurance, annual bonding premiums, vehicle registrations — these hit hard when you forget them. Load them into the week they're due.

Mistake 3: Not updating it

A forecast that sits in a spreadsheet and never gets touched is useless. Update it every Monday with actuals from last week and revised projections going forward.

What a good week looks like

Every Monday morning, you open the forecast and you can answer:

  • Can I make payroll for the next 4 weeks?
  • When is the next draw coming in?
  • Do I need to chase any AR this week?
  • Is there a cash gap I need to bridge with a line of credit?

If you can answer those 4 questions, you're running your money instead of reacting to it.

Get started

We have a free 13-week cash flow template in the Construction Vault. Download it, plug in your numbers, and start rolling it forward every Monday.

Want us to build and maintain your forecast? Book a free call — we'll show you exactly what yours looks like.

Ready to see your numbers?

Book a free 30-minute call.

You walk away with a list of leaks in your books. Free. No pitch.

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