13-Week Cash Flow Forecast
Build a rolling 13-week cash forecast from opening balance, recurring items, and one-off receipts and payments. Shows the weekly closing balance, the low point, and the week you would first go negative.
How do I build a 13-week cash flow forecast?
Start from your opening cash balance, then lay out expected receipts and payments week by week for the next thirteen weeks. Each week's closing balance becomes the next week's opening balance. Thirteen weeks is the operational standard because it is far enough ahead to change a decision and near enough that most of the flows inside it are already contracted rather than forecast. Forecast collections from how customers actually pay, not from their stated terms.
How to use this tool
- 1
Set the opening position
Cash you can actually access, excluding restricted balances and undrawn credit.
- 2
Add recurring and one-off items
Weekly or monthly recurring flows, plus specific receipts and payments in the week you expect them.
- 3
Find the low point
See the closing balance each week, the lowest point across the quarter, and the first week you would go negative.
Terms tell you when they should pay, not when they will
Four things account for most of the error in a cash forecast, and the first is the largest by a wide margin.
Forecasting collections from terms
A customer on net-30 who has paid at day 52 for the last eight invoices will pay at day 52 again. Forecasting them at 30 puts three weeks of cash in the wrong place every month. Use the median of their actual behaviour.
Missing the annual and quarterly cluster
Insurance renewals, tax payments, and annual software renewals do not appear in the normal monthly rhythm and tend to cluster. Build a calendar of them once and they stop being a surprise.
Extra pay periods
A fortnightly payroll produces three runs in some months rather than two. Forecasting payroll as a flat monthly figure guarantees being wrong twice a year, in the weeks it hurts most.
Treating profit as cash
Deriving the cash forecast from the P&L imports every accrual difference into it. Depreciation, accrued bonuses, and deferred revenue all break the link. Forecast the movements, not the earnings.
Two to four hours a week, forever
Built by hand this is a permanent weekly cost: export AR, export AP, reconcile against the ledger, apply payment profiles, roll the model forward, and compare against last week's version. That is assembly rather than analysis, and it is the same work every week. The judgement (which customer is genuinely at risk, whether a payment can be deferred) takes a fraction of the time. When the person doing it is senior enough that four hours a week displaces work only they can do, the arithmetic on automating stops being close.
See how DataWyse answers thisQuestions finance teams ask about this tool
What is a 13-week cash flow forecast?
A rolling weekly projection of cash receipts and payments across the next quarter. Thirteen weeks is the convention because it is far enough ahead to act on and near enough that most invoices, payroll runs, and supplier payments in the window are already known rather than estimated.
How accurate should a cash forecast be?
Around 5% at the total level in the first four weeks, widening after that. Near-term accuracy is mostly a data-quality question since those flows are largely known. Further out it depends on collections behaviour and new sales, and no process makes those precise.
How often should I update it?
Weekly. Drop the week that closed, add a new week thirteen, and compare last week's forecast against what actually happened before re-forecasting. The variance explanation is often more useful than the forecast itself, because it surfaces customers whose behaviour is drifting before it appears in the aging report.
Should the forecast include undrawn credit?
Track it separately rather than adding it to the opening balance. A facility is real optionality, but it carries covenants and can be reduced exactly when conditions deteriorate. Forecast on cash, and note available credit alongside.
Why is my cash forecast always wrong?
Most often because collections are forecast from payment terms rather than from actual customer behaviour, and because annual or quarterly payments falling outside the monthly rhythm were missed. Both are fixable, and together they account for the majority of forecast error in mid-market teams.
Is this tool really free?
Yes. No signup, no email required, no usage limit. It runs entirely in your browser: nothing you type is uploaded to a server or stored anywhere. We build these because the people who find them useful are the people who eventually need a financial analyst that works the same way.
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