Profit tells you whether the business works. A 13-week forecast tells you whether you can pay everyone on Friday.
A 13-week cash flow forecast projects actual cash in and out week by week using the direct method: opening cash, plus expected customer receipts, minus payroll, suppliers, tax, debt and other payments, equals closing cash. Roll it forward every week and compare forecast with actual, so you see a shortfall weeks before it happens rather than on the day.
Thirteen weeks is a quarter, short enough to forecast with real data and long enough to act on what it shows: delay a purchase, chase a customer, or talk to your bank early. Weekly columns catch the timing problems that a monthly forecast smooths over.
| Row | Source |
|---|---|
| Opening cash | Bank balances (week 1), then last week's closing |
| + Customer receipts | Receivables ageing and expected new sales |
| + Other receipts | Asset sales, refunds, funding |
| − Payroll and related taxes | Payroll calendar |
| − Supplier payments | Payables ageing and planned payment runs |
| − Rent, utilities and other fixed costs | Contracts and standing orders |
| − Tax payments | Tax calendar |
| − Loan and lease repayments | Facility agreements |
| − Capital spending | Approved purchases |
| = Closing cash | Calculated |
| Minimum cash buffer | Your policy |
| Facility headroom | Undrawn borrowing available |
The most common mistake is assuming customers pay on their terms. Use each major customer's actual payment pattern: if a customer on 30-day terms usually pays in 45 days, forecast 45. Your credit control process and DSO tell you how close to terms customers really pay.
Map supplier payments to the weeks your payment runs actually happen, not invoice due dates scattered across every day. Put payroll, tax and loan repayments on their exact dates; they are the payments you can't move.
Variances are how the forecast improves. If customer receipts are consistently overstated, your collection assumptions are too optimistic. Track the variance by row for a few weeks and adjust the assumptions, not just the numbers.
Put your tax dates in the forecast: VAT returns and PAYE payments in the UK; payroll tax deposits, sales tax and estimated tax payments in the US.
Work out DSO and the cash tied up in late payers. Free to use online.
The Cash Flow Forecasting & Liquidity Control System tests every week of a rolling cash forecast against your minimum cash buffer and lending covenants, and flags a breach before it lands. Excel, no macros, one-time price.
A budget plans profit by month for the year. A 13-week forecast predicts actual cash movements week by week for the next quarter, so it is much more precise about timing.
Usually finance or treasury, with inputs from sales, purchasing and payroll. One owner should update it every week.
Aim for the closing cash in the first few weeks to be close to actual. Accuracy further out matters less than spotting the trend early.
Yes, most are. Use one column per week and one row for each type of receipt and payment, with a tab that records actual cash so the variances calculate automatically.
Last updated 18 October 2026. General guidance for finance teams; check it against your own policies, systems and local rules.