You check the bank balance every morning. Some weeks it looks fine. Then wages, a supplier run and the BAS all land in the same fortnight, and the account is suddenly thinner than you expected.
A 13-week cash flow forecast fixes that. It is a simple, week-by-week view of the cash coming in and going out over the next quarter, so you see a tight week two months before it arrives. Most owners can build one in an afternoon and keep it current in 20 minutes a week.
This guide walks you through how to build one, step by step, with a worked example from a trades business heading into the Christmas shutdown.
In short:
- A 13-week cash flow forecast shows your bank balance week by week for the next quarter.
- It is built from real cash timing: when customers actually pay and when bills actually leave your account.
- Wages, super, BAS and rent are the fixed dates that cause most cash surprises, so they go in first.
- You roll it forward every week, adding a new week at the end and checking last week against what really happened.
- Its real value is the early warning: weeks of notice to chase debtors, move payments or arrange funding.
What is a 13-week cash flow forecast?
A 13-week cash flow forecast is a rolling, weekly projection of your cash position for the next quarter. Each column is one week. Each row is a type of cash in or cash out. The bottom line is your expected closing bank balance for each week.
It is different from your profit and loss. Your P&L tells you whether you made money. The forecast tells you whether you will have money in the bank on the Thursday your wages are due. Plenty of profitable businesses come unstuck on that difference, which we cover in why profitable businesses still run out of cash.
It is also a common worry. In a Tyro survey released in March 2026, 59% of Australian small business owners said they had felt cash flow stress in the previous six months.
Why 13 weeks and not 12 months?
Thirteen weeks is one full quarter, which is long enough to see trouble coming and short enough to forecast with real accuracy. You know most of the invoices that will be paid in the next few weeks. You know your wage dates, your rent and your BAS date. You do not know much about next August.
A quarter also lines up with the way Australian businesses already run. Quarterly BAS, quarterly PAYG instalments and seasonal swings all fit inside the window. Your annual budget still matters for big-picture planning. The 13-week forecast is the tool you use to run the bank account day to day.
An accountant shows you what already happened. A CFO shows you what to do next.
A weekly forecast is the most practical version of that idea. It turns your numbers into decisions you make this week.
How do you build a 13-week cash flow forecast?
You build it in a spreadsheet with 13 weekly columns, starting from today’s real bank balance and adding cash in and cash out by the week it will actually move. Here is the order we use with clients.
- Set up the sheet. Put the week-starting dates across the top (13 columns). Down the side, list cash in, cash out, net movement, opening balance and closing balance.
- Start with your real bank balance. Use the combined balance of your operating accounts today, after reconciling in Xero. If your bookkeeping is behind, catch it up first. A forecast built on old numbers is a guess.
- Enter your fixed outgoings by date. Wages on each payday, super, rent, loan and lease repayments, insurance, subscriptions and your BAS. These are the payments you cannot move, so they shape everything else.
- Add tax and super dates. Quarterly BAS is due on the 28th of the month after each quarter, with October to December due on 28 February (ATO due dates). Since 1 July 2026, Payday Super means super must reach your employees’ funds within 7 business days of each payday, so super now follows your pay cycle rather than a quarterly date.
- Forecast customer receipts by when they pay, not when you invoice. Run your aged receivables report. Put each invoice in the week you expect the money, based on how that customer really pays. If a builder always pays at 45 days, forecast 45 days.
- Add new sales. For work not yet invoiced, estimate weekly sales from your pipeline or recent averages, then push them out by your typical collection time.
- Add supplier payments. Use your aged payables for bills already received, then add an estimate for future purchases tied to your forecast sales.
- Calculate the closing balance. Opening balance plus cash in, minus cash out, equals closing balance. That becomes next week’s opening balance.
- Mark your minimum buffer. Pick the lowest balance you are comfortable holding, often around two to four weeks of fixed costs. Highlight any week that drops below it.
- Act on the red weeks. For every week below your buffer, write down what you will do about it and by when.
If you would like a head start, our free Complete Financial Clarity Excel template gives you a ready-made layout for tracking your numbers. Business Victoria also has a free cash flow forecasting template if you prefer to start from scratch.
Worked example: an electrical contractor heading into Christmas
This is an example with realistic numbers, not a real client. Picture an electrical contractor turning over about $5.5M a year, with a team of 12 on a fortnightly pay cycle. The owner builds a 13-week forecast on Monday 19 October 2026 with $90,000 in the bank.
Here is what goes in:
- Customer receipts of about $100,000 to $115,000 a week, dropping hard over Christmas when builders close.
- Net wages of $55,000 each fortnight, with a bigger $85,000 pay before Christmas to cover leave and the end-of-year bonus.
- Super of $9,000 paid the week after each payday.
- Materials and suppliers of $52,000 a week, falling to $15,000 during the shutdown.
- Overheads of $8,000 a week, plus $18,000 a month in rent and an equipment loan.
- The July to September BAS of $62,000, due 28 October.
| Week starting | Cash in | Cash out | Closing balance |
|---|---|---|---|
| 19 Oct | $105,000 | $115,000 | $80,000 |
| 26 Oct (BAS due) | $100,000 | $149,000 | $31,000 |
| 2 Nov | $110,000 | $115,000 | $26,000 |
| 9 Nov | $105,000 | $69,000 | $62,000 |
| 16 Nov | $100,000 | $115,000 | $47,000 |
| 23 Nov | $105,000 | $87,000 | $65,000 |
| 30 Nov | $105,000 | $115,000 | $55,000 |
| 7 Dec | $110,000 | $69,000 | $96,000 |
| 14 Dec (Christmas pay) | $115,000 | $145,000 | $66,000 |
| 21 Dec | $60,000 | $90,000 | $36,000 |
| 28 Dec | $15,000 | $78,000 | minus $27,000 |
| 4 Jan | $40,000 | $32,000 | minus $19,000 |
| 11 Jan | $80,000 | $115,000 | minus $54,000 |
The business is profitable the whole way through. Yet by early January the account is $54,000 overdrawn, because wages keep running while builders stop paying for the holidays.
The value is the timing. The owner sees this in October, with 10 weeks to act. Here is the plan they make:
- Send December progress claims by 1 December instead of month end, so builders pay before they close. Forecast effect: about $45,000 that would have arrived in late January now lands in December.
- Chase two slow builders who owe $38,000 between them. Both are more than 60 days overdue and were left out of the forecast.
- Agree with the main wholesaler to pay the December account in late January. Forecast effect: about $25,000 moved out of the danger zone.
- Talk to the bank in November, not on Christmas Eve, about a small overdraft as a safety net.
With the first three actions in place, the mid-January balance moves from minus $54,000 to roughly plus $54,000. Same profit, same work, very different January. The forecast also flags a second, smaller squeeze: the BAS week in late October takes the balance down to around $26,000, so the owner holds off on a planned ute purchase until December.
How do you keep the forecast accurate each week?
You keep it accurate with a short weekly review: roll it forward one week, compare last week’s forecast with what actually happened, and fix the assumptions that were wrong. It takes about 20 minutes once the habit is set.
The weekly routine
- Reconcile the bank in Xero so last week’s actuals are complete.
- Replace last week’s forecast numbers with the actual figures.
- Note any gap over about 10% and ask why. Was a customer late? Did a bill come early?
- Update receipts using the latest aged receivables report.
- Add a new week 13 at the end, so you always see a full quarter ahead.
Common mistakes to avoid
- Forecasting receipts by invoice date instead of payment date.
- Forgetting the GST inside your receipts belongs to the ATO at BAS time.
- Leaving out annual costs like insurance, registrations and WorkCover premiums.
- Being optimistic about new sales. Forecast what is likely, then plan for a slower case.
- Building it once and never updating it.
Who should build it: your bookkeeper, accountant or a virtual CFO?
The best set-up is shared: your bookkeeper keeps the data clean, and a virtual CFO or proactive accountant builds the model and helps you act on it. Each role brings something different.
| Role | What they bring to the forecast |
|---|---|
| Bookkeeper | Reconciled bank accounts, up-to-date receivables and payables, accurate payroll and BAS figures. |
| Tax accountant | Tax and BAS amounts and lodgement dates, usually looking back at what already happened. |
| Virtual CFO or CFO advisor | Builds and owns the model, runs scenarios, spots red weeks early and helps you decide what to do. |
For many businesses turning over $2M to $50M, an outsourced finance team covers all three. Our bookkeeping packages keep the data current, and our virtual CFO packages include cash flow forecasting and a regular review with an advisor. Some owners call it a fractional or outsourced CFO. It is the same idea.
Across our clients we have seen an average 29% lift in profit and 17% lift in cash flow (results vary). A weekly cash forecast is usually one of the first things we put in place.
Common questions
Is a 13-week cash flow forecast the same as a budget?
No. A budget sets targets for income and expenses over a year, usually by month. A 13-week forecast predicts your actual bank balance week by week over the next quarter, based on real cash timing. You need both, but the forecast is the one that warns you about a tight week.
Can I build a 13-week forecast inside Xero?
Partly. Xero’s built-in cash flow tools are useful for a short-term view based on bills and invoices already entered. Most owners still use a spreadsheet or a forecasting app linked to Xero for a full 13 weeks, because you need to add future sales, wages and tax dates that are not in Xero yet.
How accurate does it need to be?
Aim to be within about 10% for the next four weeks and treat the later weeks as a direction, not a promise. Accuracy improves fast once you compare forecast against actual every week. The goal is to spot a problem early, not to predict every dollar.
What minimum cash buffer should I hold?
Many owners aim for two to four weeks of fixed costs, such as wages, super, rent and loan repayments. Seasonal businesses often need more going into their quiet period. The right number depends on your industry, your customers and how fast you can access funding.
Want a clear view of your next 13 weeks?
If you would like a forecast built for your business and someone to review it with you each month, book a free call with our team. You can also grab the free Excel template above to get started on your own.
Related reading
This article is general information only and doesn’t take your circumstances into account. Speak with a qualified adviser before making decisions.
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