How to Build a 12-Month Cash Flow Forecast
A 12-month cash flow forecast is a simple map of the money you expect to come in and go out over the next year. It will never be perfectly accurate, and that is fine. Its job is to show you the tight months, the big decisions and the room you have to grow, long before they arrive.
Key takeaways
- A cash flow forecast tracks when money actually moves in and out of your bank, not just when you make a sale.
- Start with today's bank balance, then estimate cash in and cash out for each of the next 12 months.
- Build in timing: when customers really pay, and when bills, taxes and annual costs really fall due.
- Run a cautious scenario alongside your expected one, so you know how much room you have.
- Update it monthly with real numbers. A forecast you revisit is far more useful than a perfect one you never open.
Most small business owners know roughly how much is in the bank today. Far fewer know what it will look like in September, or whether they can afford a new hire in the autumn, or which month the annual insurance renewal will squeeze them. That uncertainty causes stress, and it also leads to poor decisions: holding back when you could invest, or spending when a lean month is coming.
A 12-month cash flow forecast fixes that. It is not an accounting report and you do not need to be an accountant to build one. If you can use a spreadsheet and look up your bank statements, you can have a working forecast in an afternoon. Here is how.
What a 12-month forecast is (and is not)
A cash flow forecast estimates the cash that will enter and leave your business bank account each month. At the end of every month, it shows a projected closing balance. String twelve of those together and you can see the shape of your year.
It is different from a profit forecast. Profit counts a sale when you make it and a cost when you incur it. Cash flow counts money only when it actually moves. If you invoice a client in March and they pay in May, the profit lands in March but the cash lands in May. For running a small business day to day, the cash view is usually the one that keeps you safe.
It is also different from a short-term, week-by-week model. A 13-week cash flow model is useful when cash is tight and you need detail. A 12-month forecast is the bigger picture: monthly, broader and focused on planning ahead.
Common mistake
Building the forecast from your sales targets instead of your bank. Targets are hopes. A forecast should start from cash you actually have and money you can reasonably expect. Keep the ambitious version as a separate scenario, not your main plan.
Before you start: gather these numbers
A little preparation makes the build much faster. Pull together:
- Your current bank balance across all business accounts.
- The last 12 months of bank statements or an export from your accounting software.
- Your list of regular bills: rent, payroll, loans, software, insurance and anything paid monthly, quarterly or yearly.
- Known tax dates for your country, such as US quarterly estimated taxes or UK VAT and self-assessment payments. Check the current dates with the official tax authority.
- Customer payment habits: how long, on average, your customers take to pay.
- Any planned changes: new hires, price changes, equipment purchases, a new product or a contract ending.
How to build it, step by step
Open a spreadsheet and set up 12 columns, one for each month, starting with next month. Then work down the rows.
- Enter your opening balance. The first month's opening balance is today's real cash. Every later month's opening balance is the previous month's closing balance.
- Forecast cash in. List each source of income on its own row: product sales, services, subscriptions, deposits, grants or loan funds. Estimate the amount you expect to receive each month, not what you expect to bill.
- Forecast cash out. List each cost on its own row. Group them if you like: stock and direct costs, payroll, rent and overheads, marketing, loan repayments, taxes, and one-off purchases.
- Calculate net cash flow. For each month, total cash in minus total cash out.
- Calculate the closing balance. Opening balance plus net cash flow. Carry it across as next month's opening balance.
- Set a minimum balance line. Decide the lowest balance you are comfortable holding, and highlight any month that dips below it.
- Review the shape. Look for the lowest month, the biggest outflows and any stretch where the balance falls several months in a row.
Pro tip
Use history to set your sales estimates. Look at the same month last year, then adjust for anything that has changed, such as new prices or new customers. This captures seasonal patterns automatically, which a flat monthly guess never will.
Getting the timing right
Timing is where most forecasts go wrong. The total for the year might be correct, but if a big payment lands in the wrong month, the forecast will tell you a tight month is fine.
Customer payments
If you invoice on 30-day terms but customers usually pay in 45 days, use 45. Look at your actual payment history rather than your stated terms. For card or cash sales, money usually arrives within days, so you can treat it as same-month cash.
Annual and quarterly costs
Insurance renewals, annual software, professional memberships and accountancy fees often arrive in lumps. Put each one in the month it is actually due, not spread evenly across the year. Spreading them hides the squeeze.
Taxes
Tax payments are some of the largest and most predictable outflows. Add every known tax date for the next 12 months. If you are unsure of an amount, use last year's figure as a starting point and confirm with your accountant.
Seasonal costs
Think about what your year looks like. Retailers may buy stock months before a busy season. Service firms may pay holiday cover in summer. A forecast built in spring should already reflect the summer months and the year-end period.
A 12-month cash flow forecast template
Here is the basic layout. Your spreadsheet will have 12 month columns; this example shows three to keep it readable. All figures are made-up examples.
| Row | May (example) | June (example) | July (example) |
|---|---|---|---|
| Opening balance | $20,000 | $21,500 | $17,300 |
| Cash in: customer payments | $14,000 | $15,000 | $13,500 |
| Cash out: payroll and contractors | $8,000 | $8,000 | $8,500 |
| Cash out: rent, software and overheads | $4,000 | $4,000 | $4,000 |
| Cash out: taxes and annual bills | $500 | $7,200 | $1,800 |
| Net cash flow | $1,500 | -$4,200 | -$800 |
| Closing balance | $21,500 | $17,300 | $16,500 |
In a real forecast you would split cash in and cash out into more rows, so you can see exactly where each change comes from. Keep the totals and the closing balance calculated with formulas so the whole sheet updates when you change one number.
Plan for more than one outcome
Your first forecast is your best guess. But businesses rarely follow the best guess. Building two or three versions gives you a much clearer sense of risk.
- Expected case: your realistic estimate, based on history and known changes.
- Cautious case: sales a bit lower, customers paying a bit later, and one or two costs a bit higher.
- Growth case: optional, if you are planning an investment such as a new hire, and want to see when it pays for itself.
Example
Imagine Sam, who runs a two-person web design studio. His expected forecast shows a healthy balance all year. But in his cautious case, where two big clients each pay a month late, the balance drops below his minimum in August and October. That tells him two things: he should ask for deposits on large projects, and he should wait until November before hiring the junior designer he has in mind. The forecast did not stop him from growing. It helped him choose the right moment. (This scenario is made up for illustration.)
Keep it alive: the monthly update
A forecast is a living document. The real value comes when you update it every month and compare what happened with what you expected.
- Replace last month's forecast with actual figures from your bank or accounting software.
- Note the biggest differences between forecast and actual. Did a customer pay late? Did a cost rise?
- Adjust the coming months based on what you learned.
- Add a new month at the end, so you always look a full 12 months ahead. This is called a rolling forecast.
- Check the low points again and decide whether any action is needed now.
This monthly routine usually takes 30 to 60 minutes once you are set up. Over time, your forecasts will get noticeably more accurate, because you will learn your business's real rhythms.
Do you need special software?
Not to start. A spreadsheet in Google Sheets or Microsoft Excel works well for most small businesses. As you grow, dedicated cash flow forecasting tools such as Float, Fathom or Pulse can connect to your accounting software and build forecasts from live data. Check their current features, pricing and privacy policies before connecting your accounts, and remember that a tool only helps if you still review the numbers yourself.
Common mistake
Forgetting the owner. If you pay yourself through drawings or a salary, put it in the forecast as a regular outflow. Otherwise the business will look more comfortable than it really is, and you may end up skipping your own pay in a tight month.
A brief note: this guide is general information, not financial or tax advice. If you plan to use your forecast to support a loan application, investment or major decision, it is worth reviewing it with an accountant who knows your business.
Your 12-month forecast action plan
- Gather your bank balance, statements, bills and tax dates
- Set up a spreadsheet with 12 monthly columns
- Enter today's balance as the first opening balance
- Forecast cash in by source, based on when customers really pay
- Forecast cash out by category, with annual bills in the right month
- Set a minimum balance and highlight months below it
- Build a cautious scenario alongside your expected one
- Book a monthly update and roll the forecast forward
Frequently asked questions
How accurate does a 12-month cash flow forecast need to be?
It does not need to be exact. The goal is to spot trends, tight months and big decisions early. Expect the near months to be fairly accurate and the later months to be rougher. Monthly updates steadily improve accuracy.
What is the difference between a cash flow forecast and a budget?
A budget sets targets for income and spending, usually on a profit basis. A cash flow forecast predicts when money will actually move in and out of the bank. Many businesses use both: the budget for goals and the forecast for staying solvent.
Should I include VAT or sales tax in my forecast?
If you collect VAT or sales tax, the cash passes through your bank, so many owners include it in cash in and then show the payment to the tax authority as cash out. Ask your accountant which approach fits your setup.
What should I do if my forecast shows a shortfall?
Act early. Options include chasing late payments, asking for deposits, delaying non-essential spending, talking to suppliers about terms, or arranging financing before you need it. The earlier you see the gap, the more choices you have.
Related reading
The bottom line
A 12-month cash flow forecast turns the year ahead from a guess into a plan. Start from your real bank balance, estimate cash in and out month by month with honest timing, mark the months that dip too low, and test a cautious version alongside your expected one.
Then keep it alive with a short monthly update. Within a few months you will know your business's cash rhythm far better, and you will make bigger decisions with a lot more confidence.
