How to Forecast Cash Flow: A Guide for Small Business

Cash flow forecasting is the process of estimating how much cash you expect to come into and go out of your business over the coming weeks or months. A cash flow forecast helps predict whether you’ll have enough money available to pay bills as they fall due and highlights potential cash shortages before they become a problem.

Learning how to forecast cash flow is mainly about timing. Unlike a budget or profit and loss statement, a cash flow forecast focuses on when money actually reaches or leaves your bank account rather than whether the business is profitable overall.

For a small business, a useful forecast usually starts with expected customer payments, upcoming expenses and the opening cash balance, then projects the resulting cash position for each week or month ahead.

This article provides general information only and isn’t intended as personal financial advice. Every business is different, so if you’re unsure how forecasting applies to your situation, speak with your accountant or business adviser.

Key takeaways:

• A cash flow forecast estimates cash timing, not profitability — a business can be profitable on paper and still run short of cash on a specific day.
• It’s built from three parts: cash incoming, cash outgoing, and the resulting cash balance for each period.
• Common forecast horizons are a detailed 4-13 week view alongside a rolling 12-month picture, though the right horizon depends on how seasonal or variable the business is.
• Tax obligations — GST, PAYG withholding, PAYG instalments and super — are real cash outflows that belong in the forecast, not just supplier and wage payments.
• A forecast is only useful if it’s checked against actual results and updated regularly — a forecast built once and never revisited loses accuracy fast.
• Free templates from business.gov.au are a reasonable starting point; accounting software can speed up the process once bank feeds and invoicing are already set up.

What is a cash flow forecast?

A cash flow forecast is an estimate of future cash coming into and going out of the business, used to work out whether there’ll be enough cash on hand to cover upcoming costs. It’s forward-looking — a bank statement or cash flow report tells you what already happened, while a forecast is an estimate of what’s coming, built from what you’ve seen in the past, what you already know is coming, and your best estimate of everything else.

The basics are the same whether you’re a sole trader, a company or a startup. The main difference is that newer businesses have less historical data to base their forecasts on.

Why cash flow forecasting matters more than it seems

A lot of small business owners assume that if the business is profitable, cash flow will naturally take care of itself. It often doesn’t. It’s common to see a business that looks solidly profitable on its year-end figures but spent several months during the year genuinely short of cash — because a big invoice was paid late, or a large expense landed before the income tied to it arrived. Profit and cash are related, but they’re not the same thing. A cash flow forecast focuses on the one that determines whether you can actually pay your bills when they’re due.

Cash flow forecast vs budget vs profit and loss statement

These three get confused with each other often enough to be worth separating clearly:

A business can be under budget, profitable on its P&L, and still short of cash in a given week if the timing of receipts and payments doesn’t line up — which is exactly the gap a cash flow forecast is built to catch.

What should a cash flow forecast include?

A cash flow forecast should include three core figures for each period: the cash available at the beginning, the money expected to come in, and the money expected to go out. Together, these figures show the amount of cash the business is predicted to have left at the end of the week or month.

Typical items include customer payments, supplier bills, wages and super, rent, loan repayments, subscriptions, tax obligations and irregular costs such as insurance or equipment purchases.

The closing cash balance for one period becomes the opening balance for the next. This is what allows the forecast to show how today’s expected receipts and payments could affect your cash position several weeks or months from now.

For example: say a business starts the week with a $5,000 cash balance, expects $8,000 in customer payments during the week, and has $9,500 in supplier payments, wages and rent due. The week’s net cash movement is -$1,500, which brings the closing balance down to $3,500 — and that $3,500 becomes the opening balance for the following week’s forecast.

What to include in cash incoming

Cash incoming covers everything expected to land in the business’s bank account — customer payments (based on when they’re realistically expected to arrive, not just when the invoice is issued), any loan or finance drawdowns, asset sales, and other cash injections. Looking at how customers have actually paid in the past usually produces a more realistic forecast than assuming every invoice will be paid exactly on its due date.

What to include in cash outgoing

Cash outgoing covers every payment the business expects to make — supplier and stock payments, wages and super, rent, loan repayments, subscriptions, and periodic obligations like insurance renewals. This is also where GST, PAYG withholding, PAYG instalments and superannuation belong, since they’re real cash leaving the business on a schedule tied to BAS due dates rather than evenly through the month. Our BAS explained guide covers those due dates in more detail if you’re mapping them into a forecast for the first time.

Choosing a forecast horizon and update frequency

There’s no single correct time horizon. A short, detailed forecast — commonly 4 to 13 weeks — is useful for spotting an imminent shortfall with enough warning to act. A longer, rolling 12-month view is more useful for seeing the bigger seasonal picture and planning around known slow periods. Businesses with seasonal income or expenses — such as retail or hospitality — often get the most value from forecasting across a full seasonal cycle instead of just a few weeks ahead. How often to update it depends on how quickly the business’s cash position can move: weekly for a tight cash position, monthly for something more stable.

How to do a cash flow forecast step by step

If you’re wondering how to forecast cash flow, the process is relatively straightforward: start with the cash you have available, estimate when money will come in, list when payments will go out, and calculate the resulting balance for each period.

You don’t need to predict every figure perfectly. The aim is to build a realistic picture of your likely cash position and then improve the forecast as actual results come in.

business.gov.au provides a free cash flow statement template that covers this structure and is a reasonable starting point instead of building a spreadsheet from scratch.

Common cash flow forecasting mistakes

• Assuming invoices get paid exactly on their due date, rather than basing the forecast on how customers actually tend to pay.
• Leaving out tax and super obligations, which understates cash outgoing around BAS periods and payday super deadlines.
• Building a forecast once and never comparing it with actual results, which lets inaccurate assumptions carry forward unnoticed.
• Forecasting too far ahead in too much detail, when a shorter, more accurate near-term view is often more useful than a long speculative one.
• Ignoring irregular but predictable costs — insurance renewals, equipment replacement, annual subscriptions — that don’t show up in a typical month but still need to be planned for.

What does a cash flow forecast predict?

A cash flow forecast predicts your expected cash position over a future period, including when you may have a surplus or face a potential shortfall.

The real value of a cash flow forecast isn’t the spreadsheet itself — it’s the early warning it gives. A forecast that shows a cash shortfall six weeks out gives real options: chase overdue invoices, delay a non-essential purchase, arrange finance, or talk to a supplier about payment terms. The same shortfall discovered the week it happens leaves far fewer options and usually means scrambling rather than choosing.

Software and tools that help

Accounting software such as Xero can make forecasting easier once your bank feeds, invoices and bills are up to date, with some platforms able to project near-term cash flow from unpaid invoices and bills already sitting in the system. Software can save time, but the forecast is only as accurate as the assumptions behind it — especially when customers actually pay rather than when invoices are due.

Getting help

If you want a clearer picture of your business’s cash position before cash flow becomes a problem, our business advisory and virtual CFO services can help you build practical cash flow forecasts and make more confident financial decisions using your actual bookkeeping data rather than a generic template.

A forecast tells you where the gaps are; closing them is a separate job. Our guide to how Melbourne businesses improve cash flow covers the levers — debtor days, invoicing timing, eInvoicing, GST accounting basis, PAYG instalment variations and low-cost dispute resolution in Victoria.

Official resources

• Cash flow — business.gov.au
• Set up a cash flow statement — business.gov.au