Build a practical 13-week cash flow forecast using dated receipts, committed payments, weekly balances and a delay scenario that exposes funding gaps.
Short answer: Start with the cash cleared in your bank today, then list every receipt and payment in the week it is realistically expected to clear for the next 13 weeks. Calculate a closing balance for each week, roll that into the next week, and test what happens when your largest uncertain receipt arrives two weeks late. Update the forecast every Friday, and act as soon as any tested balance falls below zero or below the cash buffer you need to keep trading.
A monthly budget can show that your business ought to be solvent while hiding a five-day gap that stops wages or a supplier payment. Timing is the issue. Thirteen weeks is short enough for named invoices and bills to be visible, but long enough to expose several payroll, rent, tax and supplier cycles.
Use the Four-Status Cash Roll
The Four-Status Cash Roll gives every cash line one evidence status before it enters your forecast. The four statuses are cleared, committed, expected and possible. Only the first three belong in the base forecast, and an expected receipt needs a named payer and a defensible clearing date.
- Cleared: What qualifies: Money already available in the bank; Treatment in the base forecast: Use as the opening balance only; Example: £9,400 cleared on Friday
- Committed: What qualifies: An amount and payment date are contractually or operationally fixed; Treatment in the base forecast: Include in its expected clearing week; Example: Monthly rent collected by direct debit
- Expected: What qualifies: A specific invoice or bill has a realistic date, supported by normal behaviour or confirmation; Treatment in the base forecast: Include on that date, then test a delay; Example: Customer invoice due next Thursday
- Possible: What qualifies: A quote, lead, provisional order or avoidable purchase has no dependable date; Treatment in the base forecast: Exclude from the base case; Example: Proposal awaiting approval
Build the forecast in seven steps
1. Fix a weekly cut-off
Choose one forecasting day, usually Friday afternoon after transactions have cleared. Label the next 13 columns by week-ending date, not “week one” through “week thirteen”. Dates make overdue assumptions conspicuous.
Use the cleared bank balance at that cut-off. Do not add unused overdraft capacity or a card limit to cash. Those are possible sources of finance, with costs and conditions, not money you own.
2. Enter receipts by clearing date
List customer receipts individually when they are large enough to change a decision. Use the date the money should reach your bank, which may be later than the invoice due date if the customer follows a payment run.
For small recurring receipts, grouping can be sensible. A café could use a conservative weekly card-settlement figure based on recent trading, while still separating a large catering invoice. Remove VAT or other amounts only if your forecast treats the related tax payment separately and consistently. Never mix gross receipts in one week with net receipts in another.
3. Enter payments by obligation
Start with payments that keep the business legal and operating: wages, payroll liabilities, tax, rent, loan repayments, essential suppliers and insurance. Then add committed purchases and owner drawings. Put each item in the week cash leaves the bank.
Separate optional spending. An equipment purchase that can be postponed should appear as a decision line, not be buried among unavoidable bills. That lets you see whether delaying it actually solves a shortage or merely moves the problem.
4. Calculate the weekly roll
The arithmetic is deliberately simple: closing cash = opening cash + receipts - payments
The closing cash in one week becomes the next week's opening cash. Check all 13 transitions. A single copied balance error can distort every later week.
5. Mark the lowest point
The most useful number is not the week 13 closing balance. It is the lowest balance reached anywhere in the period, often called the cash trough. Compare it with the minimum buffer your business needs.
Set that buffer from real obligations. If your unavoidable weekly outgoings are £4,000 and you need one week's cover, use £4,000. Do not choose a round number merely because it looks prudent. A forecast that stays positive but falls to £200 may still require action if one refund or repair would stop trading.
6. Run one hard delay case
Move your largest expected receipt two weeks later without moving any payments. Recalculate every affected closing balance. This test is more useful than applying a vague percentage reduction to all sales because it shows a recognisable event and the exact week it hurts.
You can add a second case for a known risk, such as a quarterly tax payment being higher than estimated. Keep each case separate. Combining five fears into one extreme scenario makes it hard to know what action would help.
7. Record actions beside the affected week
Every shortfall needs an owner, a date and an amount. “Improve cash flow” is not an action. “Ask Customer A on Monday to confirm the £7,200 payment run”, “move the £2,000 equipment deposit to week seven”, and “agree a £5,000 facility before week three” are actions you can verify.
Worked example: CedarLine Mobile Welding
CedarLine Mobile Welding starts on Friday with £9,400 of cleared cash. Its owner enters named customer receipts and scheduled payments for the next 13 weeks. These illustrative figures exclude merely possible quotes.
- 1: Opening cash: £9,400; Receipts: £4,800; Payments: £6,100; Closing cash: £8,100
- 2: Opening cash: £8,100; Receipts: £3,200; Payments: £4,500; Closing cash: £6,800
- 3: Opening cash: £6,800; Receipts: £0; Payments: £5,900; Closing cash: £900
- 4: Opening cash: £900; Receipts: £7,200; Payments: £4,000; Closing cash: £4,100
- 5: Opening cash: £4,100; Receipts: £1,800; Payments: £5,200; Closing cash: £700
- 6: Opening cash: £700; Receipts: £6,500; Payments: £4,300; Closing cash: £2,900
- 7: Opening cash: £2,900; Receipts: £4,000; Payments: £3,800; Closing cash: £3,100
- 8: Opening cash: £3,100; Receipts: £7,200; Payments: £5,100; Closing cash: £5,200
- 9: Opening cash: £5,200; Receipts: £2,600; Payments: £4,000; Closing cash: £3,800
- 10: Opening cash: £3,800; Receipts: £8,000; Payments: £6,200; Closing cash: £5,600
- 11: Opening cash: £5,600; Receipts: £3,500; Payments: £4,400; Closing cash: £4,700
- 12: Opening cash: £4,700; Receipts: £6,000; Payments: £5,000; Closing cash: £5,700
- 13: Opening cash: £5,700; Receipts: £4,400; Payments: £3,900; Closing cash: £6,200
The base forecast ends at £6,200, but that apparently comfortable result hides a £700 trough in week five. CedarLine needs a £3,000 operating buffer, so it already has a £2,300 buffer shortfall even though cash never becomes negative.
Now move the £7,200 receipt from week four to week six. Week four closes at £900 + £0 - £4,000 = -£3,100. Week five then closes at -£3,100 + £1,800 - £5,200 = -£6,500. When the delayed receipt joins the planned £6,500 in week six, closing cash recovers to -£6,500 + £13,700 - £4,300 = £2,900.
The delay creates a £6,500 cash deficit, not a profitability problem. Against CedarLine's £3,000 operating buffer, the full funding-and-buffer shortfall is £9,500. CedarLine has several weeks to confirm the customer's payment run, reschedule discretionary spending, accelerate another invoice or arrange suitable finance. Waiting for the bank balance to fall would remove most of those choices.
Keep the forecast operational
Do not rebuild the sheet from memory each week. Replace the old opening balance with the cleared bank figure, compare forecast transactions with what actually happened, move missed items to a new evidence-based date, and add a new week 13.
Investigate differences that change decisions. If three customers repeatedly pay seven days later than their stated terms, change their expected dates. If supplier direct debits vary, use the known bill when available and a cautious recent amount otherwise. Forecast accuracy improves through corrected behaviour assumptions, not more decimal places.
Your base case should be the most defensible timing view, not the average of hope and disaster. Some practitioners prefer probability-weighting receipts. That can help portfolio modelling, but for a small firm's 13-week control forecast it often creates cash that no customer will actually pay. Use dated base and delay cases instead.
Related guides
What to do in the next 90 minutes
First, download nothing and start with your bank, aged invoices, supplier bills, payroll dates, tax account and existing commitments. Record today's cleared balance and label 13 week-ending dates. Allow 20 minutes.
Next, classify every material receipt and payment through the Four-Status Cash Roll. Exclude possible sales, assign realistic clearing dates to expected receipts, and calculate each weekly closing balance. Allow 40 minutes.
Then identify the lowest balance and compare it with your operating buffer. Move the largest uncertain receipt two weeks later, recalculate the affected weeks, and write one dated action beside every breach. Spend the final 30 minutes confirming the first action. Repeat the roll every Friday.
Frequently asked questions
Why does the forecast cover 13 weeks rather than 12 months?
Thirteen weeks usually gives you a better operating view because most entries can still be tied to invoices, payroll runs, rent dates, tax obligations and known supplier orders. A 12-month forecast remains useful for strategy and funding, but its later months rely more heavily on sales assumptions.
Use both for different decisions. Run the 13-week forecast weekly for cash control, then maintain a separate monthly view for the year. If your business has unusually long lead times, such as importing seasonal stock, add a longer monthly forecast without weakening the detailed 13-week roll.
Should I include sales that I expect but have not won yet?
No, keep unconfirmed sales out of the base forecast. Classify them as possible and show them separately if they would materially change a decision. Once you have a firm order, a defined amount and a defensible payment date, move the receipt into expected or committed status.
This approach may make the base case look harsh, but it prevents speculative revenue from funding real bills on paper. For high-volume retail businesses, you can use a conservative recurring receipts assumption based on recent cleared settlements, provided you review it weekly and reduce it when current evidence weakens.
Do I use invoice dates, due dates or bank dates?
Use the date cash is likely to clear in your bank. The invoice date starts the commercial process, and the due date states the contractual expectation, but neither guarantees the clearing date. Check each large customer's payment habits and payment-run timetable.
If a reliable customer pays invoices on the last working day of each month, reflect that even when the nominal due date falls earlier. Keep the stated due date in your receivables record so lateness remains visible. The forecast date predicts liquidity; it does not excuse a customer from complying with agreed terms.
Where do VAT and other tax payments go?
Put each expected tax payment in the week it should leave your bank, using your current records and official account rather than a guessed percentage. If receipts and payments are entered gross, keep the related tax cash movement visible as a separate line. If you use net amounts, apply that treatment consistently throughout.
Tax dates and calculations vary by country, business structure and tax type, so confirm your position with the relevant authority or a qualified local accountant. A tax reserve in another bank account is still business cash, but mark it as restricted rather than available for operations.
Should an overdraft be part of the opening balance?
No, show only cleared cash as the opening balance and display an agreed overdraft separately as available financing. This keeps the forecast honest about when you begin borrowing and how much headroom remains.
For example, a closing cash line of negative £3,000 against a £10,000 agreed facility means you are using £3,000 and have £7,000 of nominal headroom, subject to the facility's conditions. Include interest and fees as payments. If the bank can review or withdraw the facility, do not treat its full limit as a permanent cash buffer.
How often should I update a 13-week forecast?
Update it once a week on the same day, and also after any event large enough to change a payment decision. A Friday roll suits many businesses because most of the week's transactions have cleared, but choose a day that matches your cycle.
Reconcile the opening balance to the bank, replace assumptions with actuals, move delayed items, and add a new final week. During a cash squeeze, update daily for the next two weeks while retaining the weekly 13-week structure. More frequent editing is useful only when new evidence changes dates or amounts.
What should I do when one week turns negative?
Act from the earliest controllable event, not from the negative week itself. Confirm major receipt dates first, chase undisputed overdue invoices, pause optional spending and ask suppliers about timing before a payment is missed. Then quantify any remaining gap and the exact period for which funding is needed.
If borrowing is appropriate, arrange it while the evidence is clear and before the shortage becomes urgent. Do not move bills to later columns merely to remove the red number. A changed date belongs in the forecast only after you have agreed or substantiated it.
Comments (0)