How to build a 13 week cash flow forecast

A job can carry a healthy margin and still empty your bank account if the money arrives in the wrong order. You pay trades weekly or fortnightly, buy materials before the work and cover wages while you wait for stage claims. A rolling forecast of the next 13 weeks, about ninety days, shows you the gap before it turns into a missed payroll.¹

1. Set up the sheet

Use a spreadsheet or the cash flow module in your accounting software. Put 13 weekly columns across the top, starting from this week. Down the side, list money in by job, then money out by type. At the top, enter today’s bank balance as the opening figure, and have each week’s closing balance carry into the next week.

Done looks like: a sheet with 13 weeks, an opening balance and a running closing balance for each week.

2. Load the money coming in from your schedules

Take each job’s build schedule and put every progress claim in the week you expect the stage to finish, plus the time the customer or their bank takes to pay. A New Zealand custom builder forecasts claims up to 12 months ahead from his schedules, about seven claims per home, and updates them every week as the schedules move.²

Be honest about timing. Do not count the deposit on a job that has not signed. Treating the next job’s deposit as a buffer for the current one works until that job is delayed.¹ Add retentions held by others as their own line with a release date, and keep a register so they are not forgotten.³

Done looks like: every expected claim for the next 13 weeks sits in a week, by job, with retentions listed separately.

3. Load everything going out

List what leaves the account and when:

• trade invoices on their actual payment terms
• supplier accounts, including materials bought before the work
• wages and super
• overheads such as rent, vehicles, insurance and software
• GST, PAYG and income tax, which build up whether or not the bank reflects them⁴
• loan repayments and what you draw for yourself

Costs go out continuously while claims come in on milestones that can sit weeks behind the spend.⁴

Done looks like: every week has a total out, and the closing balance for each week is calculated.

4. Run it every week at a set time

A forecast that is not updated is worse than none, because it gives false comfort. Pick a time and keep it. One builder reviews his forecast sheet daily and meets his bookkeeper every Wednesday to go through who is being paid that week.⁵ Another blocks Friday mornings for job cost tracking so invoicing is out by 1pm.⁶

Each week, roll the sheet forward one column, put in the real bank balance, move any claims that slipped and add new commitments.

The bank balance tells you where you are. The forecast tells you where you will be in eight weeks, while there is still time to do something about it.

Done looks like: the forecast is updated in the same slot every week, and the opening balance matches the bank.

5. Act on the gaps

When a week shows a low or negative balance, you have room to move if you see it early. The usual fixes:

• Send each progress claim the day the stage is complete. Claims sent a week or two late, across several jobs, add up to a real cash problem.¹
• Price and sign every variation before the work starts, so it can be claimed straight away.³
• Confirm the customer’s finance in writing before you start.³
• Stagger start dates and line up supplier terms with your claim dates.³
• Plan for a short year. One source points out builders only really have 9 to 10 earning months, with December, January and often April slow.⁷

Claim rules and payment timeframes are set by your contract and your state’s security of payment and domestic building laws, which differ between states. Check yours before you change how you claim.

Done looks like: every red week on the sheet has a named action and a person responsible.

Where to next

A cash forecast shows timing. To see whether the jobs behind it are making money, read WIP reporting explained. For the claim rules in your state, see Security of payment explained.

Footnotes

1. The Good Builder, “Running a Building Business in Australia”, The Good Builder, 2026. https://thegoodbuilder.com.au/how-to-run-a-building-business-in-australia/ ↩ ↩² ↩³

2. Caleb Adams, “Running A Business Is Like Getting Punched In The Face”, Better Builder Podcast, 2025. https://www.youtube.com/watch?v=MJhAxFreuc4 ↩

3. The Good Builder, “Cash Flow for Builders Australia”, The Good Builder, 2026. https://thegoodbuilder.com.au/cash-flow-for-builders-australia/ ↩ ↩² ↩³ ↩⁴

4. The Good Builder, “Why Good Builders Still Lose Money”, The Good Builder, 2026. https://thegoodbuilder.com.au/why-good-builders-still-lose-money/ ↩ ↩²

5. Joshua Rosinski, “How Outsourcing Administration Cut Overheads From 35% To 8%”, The Professional Builder (podcast), 2026. https://www.youtube.com/watch?v=vTe7JnQx6fg ↩

6. James Taylor, “Stop Signing Fixed Price Contracts Before You Beg Family For LOANS”, The Professional Builder (podcast), 2026. https://www.youtube.com/watch?v=R7sUdTHW05w ↩

7. The Good Builder, “From Farm Kid to Industry Leader: How Amanda Bulow Is Reshaping Construction From the Inside Out”, The Good Builder, 2025. https://thegoodbuilder.com.au/from-farm-kid-to-industry-leader-how-amanda-bulow-is-reshaping-construction-from-the-inside-out/ ↩