Business Financing Encyclopedia · Cash flow
13-week cash flow forecast: how to spot a cash shortfall early
A profitable company can still run out of cash on payroll day or when a loan payment falls due. A cash flow forecast shows when receipts will actually become available, which obligations must be paid and when additional liquidity may be needed.
26 October 2026 · Practical guide · 12 min read
What this guide gives you
- A structure for a 13-week forecast and a free CSV template.
- A worked example showing why a positive month-end balance can conceal a shortfall during the month.
- A process for checking expected receipts, available credit facilities and your cash buffer.
What is a 13-week cash flow forecast for?
It projects cash movements by week over roughly a quarter. Its purpose is to connect specific receipts and payments to bank balances. Unlike a profit and loss statement, it answers the question: “Will available cash cover the payment when it is due?”
The 13-week format is used in BDC’s practical short-term planning tools. It is a useful working horizon, rather than a statutory rule or a universal lender requirement.
If production or customer collection cycles last longer, supplement it with a longer forecast. Where exact payment dates matter, break the first few weeks into days. Do not treat a payment due on Monday and a receipt expected on Friday as if they occurred at the same time simply because they fall in the same week.
How to build a cash flow forecast in five steps
1. Establish the available opening cash balance
Reconcile cash across the bank accounts and cash holdings included in your forecast as of a single date. Identify amounts that cannot be used freely. Do not add undrawn credit facilities to cash already in the bank. Transfers between your own accounts within the forecast’s scope do not generate new cash for the business.
2. Allocate receipts to realistic collection dates
For significant receivables, record the customer, supporting document, amount, expected date, responsible person and evidence. An accepted delivery or an invoice issued does not itself mean cash has arrived. Consider actual payment behaviour and show disputed amounts separately. For sales through intermediaries, check settlement dates and deductions.
British Business Bank recommends allocating receipts to the period when cash is actually received. Turn this into a simple rule in your model: every significant receipt needs a verifiable assumption.
3. Capture payments without omissions or duplication
Include suppliers, payroll, rent, taxes, interest, principal repayments, fees, leases, investment spending and planned owner distributions. Use the company’s current documents for tax and other mandatory payment dates, rather than dates from a generic example. Do not treat depreciation as a cash payment or record the same loan repayment again under supplier costs.
4. Calculate closing balances and define a buffer
Weekly closing cash = opening cash + receipts − payments.
The next week starts with the previous week’s closing balance. Your chosen minimum balance is a management cash buffer, rather than a standard required of every business.
5. Separate the initial forecast from proposed actions
First retain a forecast before any new measures. Then add a separate version incorporating agreed changes to purchases, accelerated collections or new funding. Each action needs an amount, date, owner and status. An intention to negotiate with a supplier does not change an existing payment deadline.
Example: a customer pays late, but month-end cash is still positive
The table shows the first four weeks of an illustrative 13-week forecast. All amounts are in thousands of one currency; for a Russian company, for example, they could be thousands of roubles. Opening cash is 1,200 and the chosen minimum buffer is 500. The other nine weeks are not shown in this short example.
| Measure | Week 1 | Week 2 | Week 3 | Week 4 |
|---|---|---|---|---|
| Receipts | 800 | 1,600 | 900 | 1,700 |
| Payments | 1,300 | 1,400 | 1,200 | 1,200 |
| Closing cash | 700 | 900 | 600 | 1,100 |
In the base case, the lowest balance of 600 remains above the buffer. If a receipt of 900 moves from week two to week four, closing balances become 700, 0, −300 and 1,100. The final figure stays the same, but cash is insufficient in week three. A negative forecast balance indicates unfunded payments in the model; it does not mean a bank will automatically allow an overdraft.
Try the scenario
An illustrative four-week model. It does not calculate interest or assess credit availability. Amounts are in thousands of one currency.
Enter non-negative numbers no greater than 1,000,000,000.
Weekly closing cash: 700 · 0 · −300 · 1,100.
The facility is shown separately and is not added to the cash balances. Count it as a funding source only if drawdown conditions can be met and cash can arrive before it is needed. In the actual forecast, add drawdowns, fees, interest and repayments to their respective weeks.
A cash flow forecast template and weekly update process
Create 13 weekly columns and record each amount’s supporting evidence, owner and confirmation status alongside them. You can start with these rows:
- Available opening cash.
- Customer collections and other receipts, shown separately.
- Suppliers, staff, rent and other operating payments.
- Taxes, interest, principal repayments, fees and leases.
- Investment spending and owner distributions.
- Closing cash before new financing and the minimum buffer.
- A separate section for confirmed drawdowns, their costs and repayments.
A file containing row headings for Excel or another spreadsheet. Enter your own numbers and formulas; the CSV does not contain your data.
Set aside a regular weekly review: enter actual balances, reconcile the forecast to bank movements, reschedule events that have not occurred and add a new thirteenth week. Examine amount variances and timing variances separately. A rolling weekly review is also described in BDC’s cash flow planning guidance.
Assign a specific action to an uncertain receipt: for example, obtain the customer’s payment confirmation by Wednesday. If confirmation does not arrive, revise the scenario and the deadline for a funding decision. In a liquidity squeeze, check imminent dates more frequently than the weekly review cycle.
How to assess the funding requirement
In the illustrative downside scenario, the lowest balance before funding is −300 and the buffer is 500. Maintaining that buffer requires up to 800. If only 600 is available, 200 remains uncovered. These figures follow from the example’s assumptions and are not a recommended loan amount.
For a forecast before new financing: funding need = the greater of zero and “minimum buffer − lowest forecast cash balance”. This is an initial estimate of the peak shortfall. When adding a loan, recalculate every period with its costs, drawdown timing and repayments: funding itself changes the future forecast.
Check four questions: when is cash needed, for how long, which receipt will repay it and what happens if that receipt is late? If cash is needed before a lender is likely to decide, submitting an application alone does not bridge the gap. Also consider manageable working capital changes; rescheduling mandatory payments requires a valid basis or agreement.
If liquidity remains weak at the end of the horizon even after one-off receipts, extend the forecast. A loan may bridge a timing mismatch, while persistent cash outflows call for a separate review of the business’s economics.
Common sources of forecast distortion
- Revenue is substituted for collections. Recognised income is not always cash available for payments.
- Only a monthly total is used. It conceals shortfalls within the period.
- An undrawn facility is recorded as cash. Drawdown conditions and availability dates have not been checked.
- Internal transfers are counted as income. Consolidation then produces double counting.
- Unagreed actions are already included. The real shortfall disappears only on paper.
- The model is not reconciled to actuals. Outdated assumptions continue to influence decisions.
Frequently asked questions
Does this replace a cash flow budget?
It complements the budget with more detailed timing and near-term obligations. Link both tools to consistent source data so that differences in balances can be explained.
Are 13 weeks enough for a seasonal business?
Not always. Keep weekly detail for the coming quarter and add a forecast through the relevant seasonal cycle, including debt repayment.
Can I combine different currencies?
First track each currency and its conversion dates separately. An aggregate view requires explicit exchange-rate assumptions; a sufficient rouble equivalent, for example, does not guarantee that the required currency will be available on the payment date.
Can I give this forecast to a lender?
As supporting information, where it meets the lender’s request. Confirm the required format and document package separately; a forecast does not guarantee approval.
When to seek support
If collections are unpredictable, several loans are involved or account data does not reconcile into a single forecast, start with a financial review. NG Finance works with companies worldwide to assess cash flow, debt burden and potential funding approaches. Financing availability and terms depend on the country, company documentation and provider requirements.
Company financial analysis can be agreed as a standalone service. For an initial discussion, prepare debt schedules, receivables and payables listings and a plan of major payments. The scope depends on your objective and available data.
Discuss your company’s cash flowContinue reading
Sources and review date
Reviewed on 26 October 2026. The sources explain forecasting approaches; the calculations, scenario and working process in this article were prepared by NG Finance. The example does not replace a forecast based on a specific company’s data.