How to Build a 13-Week Cash Flow Forecast (Free Template)
A 13-week cash flow forecast is a simple spreadsheet with one column per week showing the cash you expect in, the cash you expect out, and the bank balance you'll be left with — one quarter ahead. It turns "will we make wages in week 12?" from a nasty surprise into a line on a screen you can act on months early. This guide walks through building one from a blank sheet, wiring in the Australian tax dates that cause most of the dips, and the 20-minute weekly ritual that keeps it honest.
Why 13 weeks, and why rolling
Thirteen weeks is one quarter: long enough to see a whole BAS cycle, three monthly rent payments and the January slowdown, short enough that you're forecasting from real invoices and real bills rather than hope. Go to 12 months and the numbers become guesses; go to four weeks and you'll spot the problem too late to fix it.
It's also rolling: every week you drop the week that's just finished and add a new one at the end, so you're always looking exactly one quarter ahead. For the wider system it sits inside — faster invoicing, tax set-asides, seasonal buffers — see our cash flow management guide. This page is about the forecast itself.
The template: a layout you can rebuild in 20 minutes
You don't need to download anything. Open Excel or Google Sheets and lay it out like this.
Across the top: a label column, then 13 week columns with the Monday date of each week in row 1 — "Week starting 5 Oct", "12 Oct" and so on. Add a notes column at the end.
Down the side, in four blocks:
| Block | Rows | What goes in each cell |
|---|---|---|
| Opening balance | 1 row | Week 1: actual bank balance. Weeks 2–13: a formula pointing at the previous week's closing balance |
| Receipts | One row per source, then a total | Invoices due (by expected payment date), cash and card sales, recurring income, other |
| Payments | One row per type, then a total | Wages, PAYG withholding, super, rent, suppliers, loan repayments, insurance, subscriptions, vehicles, owner drawings, BAS, PAYG instalments, income tax, other |
| Closing balance | 1 row | Formula: opening + total receipts − total payments |
Two formulas do all the work: closing balance is =Opening + TotalReceipts − TotalPayments, and each week's opening balance is =PreviousWeekClosing. Once they're linked, changing any single number ripples through to week 13 instantly.
One optional touch earns its keep: add a minimum buffer row — the balance you never want to drop below, often a fortnight's wages — and use conditional formatting to turn any closing balance under it red.
Most accounting software offers a short-term cash flow projection from your bank feed. It's a useful sanity check, but it can't see the job you haven't invoiced yet or the supplier who always chases at month-end. The spreadsheet can, because you tell it.
Step 1: Start with a real opening balance
Week 1's opening balance is your reconciled bank balance today — every business account added together, less any scheduled payments that haven't cleared. Not the balance you think you have, and not the figure in your software if it hasn't been reconciled since June. Everything downstream depends on this number being true.
If you keep a separate tax savings account, leave it out and treat transfers into it as a payment, so the forecast never counts the ATO's money as yours.
Step 2: Forecast receipts week by week
Receipts are where forecasts go wrong, and it's almost always the same mistake: entering invoices in the week they're due rather than the week they'll actually be paid.
Invoices already issued
Print your aged receivables list. Put each unpaid invoice in the week you genuinely expect the money to land, based on how that customer actually behaves. The council that always pays on day 45 goes in the day-45 week regardless of your terms. The customer who's 30 days overdue and not answering doesn't go in at all until they pay.
Cash and card sales
For a cafe, shop or trade business with walk-in work, use last year's same weeks as a base, adjusted for how this year is tracking. Without a year of history, use a conservative average of recent weeks.
Work not yet invoiced
Jobs you've won but haven't started go in at the week you'll invoice plus the customer's normal payment lag. If they usually take three weeks to pay, a job finishing in week 4 is a receipt in week 7.
Leave hoped-for sales out, or park them in a separate scenario tab. A forecast built on optimism is worse than none, because you'll trust it.
Step 3: Forecast payments, including the ATO ones
Payments are easier because most are predictable. Go through the last three months of bank statements, list every recurring outgoing with its usual date, then add the lumpy ones.
Regular payments
| Payment | Timing to enter |
|---|---|
| Wages (net of PAYG) | Every pay run, in the week you pay |
| Super guarantee at 12% | Same week as wages — since 1 July 2026 it must reach each employee's fund within 7 business days of payday (as at September 2026) |
| PAYG withholding | Monthly on the 21st if you pay monthly, otherwise with your quarterly BAS |
| Rent, loans, insurance, subscriptions | On their usual debit dates |
| Suppliers | The week you'll actually pay, based on their terms and your habits |
| Owner drawings | Every week or fortnight — don't leave yourself out |
Super is the one that's changed most: you used to hold it until 28 days after quarter end, and now it's part of every pay run. Our payday super guide explains what changed.
Tax dates to hardwire in
These create the dip in most forecasts, so put them in the exact week they fall due. For 2026-27, quarterly BAS is due on the standard dates below, or later if you lodge online or through a registered agent (as at September 2026):
| Quarter | Standard due date | Lodging online yourself |
|---|---|---|
| Jul–Sep 2026 | 28 Oct 2026 | 11 Nov 2026 |
| Oct–Dec 2026 | 28 Feb 2027 (a Sunday, so effectively 1 Mar 2027) | No extension on this quarter |
| Jan–Mar 2027 | 28 Apr 2027 | 12 May 2027 |
| Apr–Jun 2027 | 28 Jul 2027 | 11 Aug 2027 |
Monthly activity statements are due on the 21st of the following month with no online extension, and quarterly PAYG instalments share the standard BAS dates. Our BAS due dates guide has every date including the agent deadlines — fill in your actual dates, not the standard ones.
Then add the once-a-year lumps: income tax when your return is assessed, annual insurance premiums, workers compensation, licence renewals, and payroll tax if you're over your state's threshold. Ask your accountant for rough figures — an approximate lump in the right week beats a precise zero.
Step 4: Find the dip
Once every cell is filled, read along the closing balance row. Here's what a small trade business with fortnightly wages might see over the October–December quarter — wages in the odd weeks, rent in weeks 1, 5, 9 and 13, and the September-quarter BAS paid online in week 6:
| Week | Opening | Receipts | Payments | Closing |
|---|---|---|---|---|
| 1 | $22,000 | $11,000 | $13,500 | $19,500 |
| 2 | $19,500 | $9,000 | $4,000 | $24,500 |
| 3 | $24,500 | $12,000 | $13,000 | $23,500 |
| 4 | $23,500 | $7,000 | $4,500 | $26,000 |
| 5 | $26,000 | $10,000 | $12,500 | $23,500 |
| 6 (BAS) | $23,500 | $8,000 | $18,000 | $13,500 |
| 7 | $13,500 | $11,000 | $13,000 | $11,500 |
| 8 | $11,500 | $9,000 | $4,500 | $16,000 |
| 9 | $16,000 | $10,000 | $12,500 | $13,500 |
| 10 | $13,500 | $8,000 | $4,000 | $17,500 |
| 11 | $17,500 | $6,000 | $13,000 | $10,500 |
| 12 (Christmas) | $10,500 | $2,000 | $10,500 | $2,000 |
| 13 | $2,000 | $1,500 | $12,500 | –$9,000 |
Week 4 looks great. Week 13 is a $9,000 hole caused by nothing dramatic — Christmas receipts dry up while wages and rent keep going. Without the forecast, this owner finds out on the first Monday in January when the pay run bounces. With it, they've got three months' notice. The forecast doesn't fix anything; it buys you time.
Step 5: Act on what you see
Three months out you have options that don't exist three days out. Roughly in order of cost:
- Bring receipts forward. Invoice completed work today, not at month-end. Ask for deposits on new jobs. Offer a small discount for payment within 7 days on the big invoices due in weeks 10–12. Chase everything overdue — our guide to chasing unpaid invoices has scripts that work without burning the relationship.
- Push payments back. Ask suppliers for extended terms on December orders, defer a non-urgent purchase, or shift owner drawings a fortnight. Never push super or wages.
- Talk to the ATO early. If the BAS is the problem, lodge on time and set up a payment plan before the due date. The failure-to-lodge penalty for a small business is one penalty unit — $364 from 1 July 2026 — for every 28 days late, capped at five units, and interest on unpaid tax is no longer deductible (as at September 2026).
- Arrange finance before you need it. An overdraft approved in October is a tool; the same application in the week of the hole is a crisis. Lenders like forecasts — show them this spreadsheet.
Write the action in the notes column next to the week it fixes, then check next Monday whether it happened.
The weekly update ritual
A forecast that isn't updated is a historical document. Block 20 minutes at the same time every week — Monday morning, before the phone starts — and run this sequence:
- Reconcile the bank so this week's opening balance is real.
- Overwrite last week's forecast with actuals and note the biggest misses. If receipts keep landing a week later than predicted, your payment-lag assumption is wrong — fix the assumption, not just the number.
- Drop the finished week and add week 14, copying the formulas across.
- Re-date receipts that didn't arrive. Move them rather than deleting them, unless you now doubt they'll ever come.
- Add anything new: jobs won, quotes lost, a supplier price rise, a new hire's first pay run.
- Read the closing balance row against your minimum buffer. If a week fails, pick an action from Step 5 and write it down.
Do this for six weeks and the forecast will be accurate enough to trust. Do it for six months and you'll know your cash rhythm better than your bank does.
Mistakes that make forecasts useless
- Forecasting invoice due dates instead of payment dates — the biggest single source of error.
- Forgetting the GST in your receipts. One-eleventh of what lands from GST-registered sales isn't yours. Show the BAS in the right week, or sweep the GST into a separate account weekly and treat the sweep as a payment.
- Leaving out owner drawings. You need to eat; the forecast needs to know.
If you're writing a business plan or approaching a lender, the forecast slots straight into the financial section — our free business plan builder gives you the structure around it.
Key takeaways
- A 13-week forecast is a spreadsheet with weeks across the top, receipts and payments down the side, and a closing balance row that becomes next week's opening — two formulas do all the work.
- Enter receipts in the week the money will actually arrive, based on how each customer really pays, not on your invoice terms.
- Hardwire the ATO dates: quarterly BAS on 28 Oct, 28 Feb, 28 Apr and 28 Jul (later if you lodge online or through an agent), monthly obligations on the 21st, and super within 7 business days of every payday (as at September 2026).
- The forecast exists to find the dip early; once you can see it, chase receipts, defer non-essential payments, talk to the ATO before the due date, or arrange finance while you're still bankable.
- Update it every week at the same time: actuals in, finished week out, new week 13 added, receipts re-dated.
Where to get help
- ATO — help with paying for payment plans, due dates and what to do if you can't pay on time.
- business.gov.au for free finance templates and guidance on cash flow and business planning.
- ASBFEO if late-paying customers are the reason your receipts keep slipping.
- Your accountant or bookkeeper — an hour spent setting up the template, agreeing your tax set-aside percentages and estimating the annual lumps pays for itself the first time it catches a dip.
Frequently asked questions
What is a 13-week cash flow forecast?
A 13-week cash flow forecast is a week-by-week spreadsheet showing the cash you expect to receive, the cash you expect to pay out, and the resulting bank balance for each of the next 13 weeks — one quarter ahead. Each week's closing balance becomes the next week's opening balance, so any week that dips towards zero shows up in advance instead of on the day.
Why 13 weeks and not 12 months?
Thirteen weeks is one quarter, which is long enough to capture a full BAS cycle, three monthly rent runs and a seasonal slowdown, but short enough that the numbers are based on real invoices and real bills rather than guesses. A 12-month forecast is useful for planning and loan applications, but it's too coarse to tell you whether next Thursday's pay run clears.
How do I make a cash flow forecast in Excel or Google Sheets?
Put the 13 weeks across the columns and your cash lines down the rows: opening balance at the top, receipts grouped below it, then payments, then a closing balance row calculated as opening plus receipts minus payments. Link each week's opening cell to the previous week's closing cell and the whole thing recalculates every time you change a number. It takes about 20 minutes to build from scratch.
How often should I update my cash flow forecast?
Weekly, at the same time each week. Replace last week's forecast figures with the actual bank movements, drop the week that has just finished, add a new week 13 at the end, and re-date any invoices that didn't arrive when you expected. Once the template exists the update takes 15 to 20 minutes.
What should I include in the payments section of a cash flow forecast?
Everything that leaves the bank account: wages, PAYG withholding, super (now due within 7 business days of each payday), rent, loan repayments, supplier bills, insurance, subscriptions, vehicle costs, owner drawings, and the ATO payments — quarterly or monthly BAS, PAYG instalments and income tax. The tax items catch people out because they arrive in big lumps, so put them in the exact week they're due.
General information only. This guide doesn't take your personal or business circumstances into account and isn't financial, legal or tax advice. Rates and thresholds change — check the official sources linked in this guide and get qualified advice where your circumstances require it.