What is a 13-week cash flow forecast?
A 13-week cash flow forecast is a rolling, week-by-week projection of the cash coming in and going out over the next three months. Each week starts with the previous week's closing balance, adds expected receipts, subtracts expected payments and ends with a new closing balance. It tracks money in the bank, not profit.
That distinction matters more than it sounds. A profitable company can still run out of cash: customers pay late, stock is bought months before it's sold, and tax and loan repayments land in lumps. The profit and loss account spreads those items across the year. The 13-week forecast shows the week each one hits the bank.
Nor is it a budget. A budget is a plan for the year, usually monthly, set once and then compared against. The 13-week forecast is an operating tool, updated every week, that the founder, the finance lead and often the bank use to run the business in the short term.
Why 13 weeks?
Thirteen weeks is a quarter: far enough ahead to spot a problem while there's still time to act, near enough that you can name the invoice or bill behind almost every line. Beyond that, weekly detail turns into guesswork. A rolling quarter also captures monthly payroll, quarterly tax and most customer payment terms.
Because the forecast rolls forward each week, a full quarter is always in view, with no cliff edge at the end of a month. Lenders often ask for one when a business is under pressure, which is partly how the format became a standard.
You don't need a crisis to use it. The same forecast tells you when you can afford a hire or a large stock order, and how much of today's balance is genuinely spare. That last question is the starting point for deciding how much cash a business should keep in reserve.
How do you build a 13-week cash flow forecast?
Build the forecast in five steps. Start with today's actual cash balance. List expected receipts by customer and week. List payments by supplier, payroll, tax and debt. Work out each week's closing cash. Finally, draw a minimum cash line and check that every week stays above it.
Set the opening cash
Take the cleared balance of every bank account on the start date, less any overdraft in use. Check it against the bank itself, not the accounting system, which may show payments that haven't cleared.
Forecast receipts by customer and week
Begin with the unpaid sales invoices. Put each one in the week you realistically expect the money, judged by how that customer actually pays rather than by the due date. Add expected new sales on the same habits, and one-off receipts such as a tax refund only when they're certain.
Forecast payments by type
Place supplier payments in the week you plan to make them. Add payroll and payroll taxes on their real dates, then rent, sales and company taxes, loan repayments and interest, leases, and spending already committed.
Calculate closing cash
Opening cash plus receipts minus payments gives each week's closing cash, which becomes the next week's opening figure. Show any unused credit facility on its own line, so cash and headroom stay visibly separate.
Draw the minimum cash line
Set the lowest balance you're prepared to hold, for example two weeks of payroll plus essential bills. Flag every week that closes below it. Those weeks need a plan.
Payment habits make the biggest difference. Take a fictional customer on 30-day terms that has paid, on average, 52 days after invoice over the past year. Its latest invoice belongs in week 8, not week 5. Make that change for your three slowest payers and a comfortable-looking month can turn tight.
What does a 13-week forecast look like?
A 13-week forecast is a grid: weeks across the top, receipts and payments down the side, closing cash along the bottom. The illustration summarises the first six weeks for a fictional company with a $60,000 minimum cash line. Week 4 dips below it, because payroll and a quarterly tax bill land in the same week.
| Week | Opening cash | Receipts | Payments | Closing cash | Against the minimum |
|---|---|---|---|---|---|
| 1 | $120,000 | $45,000 | $38,000 | $127,000 | Above |
| 2 | $127,000 | $30,000 | $52,000 | $105,000 | Above |
| 3 | $105,000 | $40,000 | $35,000 | $110,000 | Above |
| 4 | $110,000 | $25,000 | $95,000 | $40,000 | Short by $20,000 |
| 5 | $40,000 | $55,000 | $30,000 | $65,000 | Above by $5,000 |
| 6 | $65,000 | $50,000 | $36,000 | $79,000 | Above |
Spotting that gap a month ahead changes the options. With several weeks' notice this company can chase two large invoices, agree a later date for one supplier payment, or arrange a short draw on its overdraft. Discovered in week 4 itself, the same $20,000 shortfall could mean paying staff or the tax authority late.
Illustration only: a fictional company with invented figures. A real forecast shows every receipt and payment on its own line, not weekly totals.
How do you keep a 13-week forecast accurate?
Keep the forecast accurate by rolling it forward every week and comparing it with what actually happened. Replace the week just ended with actual figures, add a new week 13 and update every line still to come. Then study the largest gaps between forecast and actual, and fix the assumptions behind them.
The weekly roll-forward
Pick a fixed slot, Monday morning for instance, and one named owner. Load the bank balances, tick off the receipts and payments that happened, and move anything that slipped into a later week. Add the new 13th week so the view never shrinks. With a settled template, the roll-forward becomes a short routine rather than a project.
Forecast against actual
Compare each week's actual receipts and payments with what the forecast said, line by line. Three columns are enough: forecast, actual and difference. Look for patterns rather than one-offs. If one customer always pays a fortnight late, move that customer's receipts in the forecast for good.
- Timing differences: the cash still arrives or leaves, just in another week. Move it.
- Permanent differences: a receipt that won't come, or a cost nobody expected. Change the forecast and look for similar items.
- Missing lines: anything that appeared in the bank but not in the forecast. Add a line so it can't surprise you twice.
What should you do when the forecast shows a cash gap?
When the forecast shows a gap, act early and work through the levers in order: speed up collections, renegotiate payment timing, release cash tied up in stock and spending, and only then draw on credit or seek new funding. Start with what you control, and talk to lenders before the gap arrives, not during it.
Collections
Chase overdue invoices by name, largest first, and check customers have everything they need to approve payment. Offer an early-payment discount only if the cash is worth the cost. In many countries the law also lets a business charge interest on late commercial payments.
Payment timing
Ask key suppliers early for a short extension or to split a large bill. Keep wages and taxes on time if you possibly can; if a tax bill can't be met, contact the tax authority before the due date, because many offer time-to-pay arrangements.
Stock and spending
Pause discretionary spending and non-urgent orders. Sell through slow-moving stock before reordering, and put off equipment that isn't essential this quarter.
Credit and funding
If a gap remains, use an agreed overdraft or facility, or discuss one with your bank. Lenders respond far better to a clear forecast shared weeks ahead than to an urgent request. For larger needs, read what lenders and investors look for in a financial model.
Whatever you decide, put each action into the forecast with an owner and a week, and check at the next roll-forward whether it happened. And be wary of anyone who offers to fix a cash gap fast in return for an upfront fee: it's a familiar loan-scam pattern, covered in our guide to investment fraud red flags.
What are the most common 13-week forecast mistakes?
The most common mistakes are using invoice due dates instead of real payment habits, forgetting lumpy payments such as tax and annual insurance, confusing profit with cash, and building the forecast once and never updating it. Each one makes the forecast look healthier than the bank balance will turn out to be.
- Placing receipts on invoice due dates rather than when each customer actually pays.
- Leaving out quarterly and annual items: taxes, insurance, licence renewals, bonuses.
- Including items that never touch the bank, such as depreciation or accruals.
- Treating sales tax collected from customers as yours to spend, when it's owed to the tax authority.
- Counting an unused facility as cash. Show it separately, and check the conditions the lender attached.
- Having no named owner. A forecast without a regular slot in someone's diary goes stale within a month.
Longer-range plans need the same discipline. The opening months of a financial model built for lenders should agree with the 13-week forecast, or the lender will ask why, and our financial modelling service keeps the two tied together.
Where can you get official help with tax and late payment?
- Your tax authority's guidance on paying a bill late or in instalments: most have an arrangement for businesses, and it's easier to agree before a payment is missed.
- Official guidance on late payment between businesses, including any statutory interest you can claim.
- Public bodies that support small businesses with late payment problems and finance options.
Rules differ by country. Use the official website for the country where your company is registered.
How can Ledgantic help?
Ledgantic builds a 13-week cash flow forecast with your team from your own bank exports and ledgers, sets up the weekly roll-forward and variance report, and helps you plan around any gap it shows. You keep the spreadsheet and a short guide to running it, and we never need logins to your bank.
That forecast is the core of our cash flow and treasury service. If it points to borrowing, our financial modelling and fundraising preparation picks up from there. Get in touch and tell us how you track cash today; a rough spreadsheet is a perfectly good starting point for the introductory consultation.