How to build a 13-week cash flow forecast for your NZ business

Most cash crises don’t arrive out of nowhere. The GST return, the provisional tax instalment, the quiet month after Christmas, the big customer on 20th-of-the-month terms — they’re all visible weeks ahead if you look. A 13-week cash flow forecast is how you look. It’s simple, it takes an hour to set up and fifteen minutes a week to maintain, and it’s the most useful financial tool a small business can have.

Why forecast cash, not profit?

Your profit and loss statement tells you whether the business is making money over a period. It doesn’t tell you whether there will be enough in the bank next Tuesday. Profit is recorded when you invoice; cash arrives when the customer pays. Expenses are recorded when incurred; cash leaves when you pay them. GST and PAYE don’t appear as costs on your P&L at all, yet they’re some of the biggest payments you make. A cash flow forecast tracks only one thing: money actually moving in and out of the bank account, week by week.

Step 1: Set up the grid

Create a spreadsheet with weeks across the top (Week 1 to Week 13, with dates) and these rows down the side: opening bank balance; cash in — customer receipts, other income; cash out — wages, PAYE and KiwiSaver, suppliers, rent, loan repayments, GST, income tax, other; net cash flow for the week; and closing bank balance, which becomes next week’s opening balance.

Step 2: Fill in cash coming in

Be realistic, not optimistic. Use your aged receivables to forecast when existing invoices will actually be paid, based on each customer’s real habits rather than the due date. Add expected new sales, and when they’ll turn into cash. Include any other receipts — asset sales, insurance payments, grants. For cash businesses like hospitality and retail, use recent weekly takings, adjusted for seasonality.

Step 3: Fill in cash going out

List every regular and one-off payment: wages on each payday; PAYE, KiwiSaver and other deductions on their due dates; suppliers based on your terms and what you actually owe; rent, power, insurance, phone and subscriptions; loan, lease and finance repayments; and planned purchases — stock orders, equipment, vehicle costs.

Step 4: Add every tax date

This is where New Zealand businesses most often get caught. Mark these in the right weeks. GST is generally due on the 28th of the month after the period ends, with the November period due 15 January and the March period due 7 May; estimate the amount using three twenty-thirds of GST-inclusive sales, minus GST on purchases. PAYE and employer deductions fall on the due dates that apply to your business. Employer KiwiSaver is included with PAYE — note that the minimum employer rate rises from 3% to 3.5% from 1 April 2026. Provisional tax, under the standard option for a 31 March balance date, falls on 28 August, 15 January and 7 May. Terminal tax is usually 7 February, or 7 April with a tax agent’s extension.

Tax	Typical timing to watch
GST	28th of the following month; 15 January and 7 May exceptions
PAYE and KiwiSaver	Your employer due dates
Provisional tax (standard, 31 March)	28 August, 15 January, 7 May
Terminal tax	7 February (or 7 April with extension)

Step 5: Find the low point

Look along the closing bank balance row. The lowest figure in the 13 weeks — especially if it goes below zero — is your cash gap. Note which week it falls in, how deep it is, how long the balance stays low, and what causes it. That tells you not just whether you need funding, but how much, when and for how long. Our Cash Flow Gap & Fast Loan Matcher does a quick version of this calculation and suggests a matching funding route.

Step 6: Decide what to do about the gap

Options include bringing cash in sooner by invoicing faster, offering incentives for early payment or chasing overdue accounts; pushing cash out later by negotiating supplier terms or rescheduling discretionary spending; trimming costs by pausing non-essential purchases; or arranging funding — a short-term loan, line of credit, invoice finance or property-secured option, sized to the gap and matched to its duration.

Because you’ve spotted the gap early, you can arrange funding calmly and on better terms. If you’d like to talk it through, start an enquiry — there’s no credit check at that stage.

Step 7: Roll it forward every week

Each week, replace the forecast for the week just gone with actual figures, add a new Week 13 at the end, and review the low point. Over time, comparing forecast with actual will make your forecasts sharper. The weekly habit is what turns a spreadsheet into an early-warning system.

Common forecasting mistakes

• Assuming customers pay on time. Use their actual track record.
• Forgetting annual costs — insurance, registrations, subscriptions, ACC levies.
• Leaving out tax. GST and provisional tax are the most common surprises.
• Ignoring seasonality. Last year’s pattern is a strong guide.
• Not updating it. A forecast that’s three weeks old is already out of date.

An illustrative example

An illustrative Nelson marine services business builds its first 13-week forecast in October. It shows a comfortable balance until mid-January, when a provisional tax instalment and the November–December GST return fall due in the same week, just as summer work is starting and customers haven’t yet paid. The forecast shows the balance dipping below zero for about four weeks. Knowing this in October, the owner arranges a line of credit in November while the account looks strong, draws on it in January and clears it by late February.

What a forecast tells a lender

When you approach a lender with a forecast, you show three things: you understand your business’s cash cycle, you know exactly how much you need and for how long, and you have a credible plan to repay. That makes approval faster and often improves the terms.

Keep it simple

Your forecast doesn’t need dozens of rows. Ten to fifteen lines that capture the big receipts and payments are enough. The value comes from updating it every week and acting early on what it shows.

Turn your forecast into a plan

If your forecast shows a gap coming, let’s work out the best way to cover it before it arrives. No credit check is run when you first enquire, your information stays with us instead of being spread across lenders, and a real person will help match the funding to the shape of your gap.

Please share accurate figures on the form — the gap, when it hits and how long it lasts — so we can match you properly the first time. Plan your funding now.