13-week cash flow model: how to build it, a worked example, and an Excel template

A 13-week cash flow answers one question: in which week does cash run lowest, and is that below the balance the company has to keep? This page builds one on a worked example and gives a free Excel template for a company's finance team to run every week.

What a 13-week cash flow is, and who asks for one

It is a weekly forecast of cash for the next quarter, built by the direct method: the actual receipts and payments expected, line by line, rather than profit adjusted for non-cash items. It rolls forward every week. The Turnaround Management Association describes it as a short-term planning tool that projects inflows and outflows over a rolling 13-week period, used by CFOs, controllers, lenders and their advisors.

Lenders, boards and turnaround advisors ask for one when liquidity is tight. Thirteen weeks is one quarter: long enough to catch the payroll cycles, a quarterly tax payment and most supplier terms, and short enough that most of it comes from invoices, bills and schedules that already exist. The Association for Financial Professionals notes that the receipts and disbursements method works best for short-term forecasts and is only as reliable as the underlying data. That is the reason to build the receipts line from the receivables ledger, not from a sales target.

The lines you need

Each week: closing cash = opening cash + receipts − disbursements + draws − repayments, and the next week opens at that figure.

Worked example: eight of the thirteen weeks

Opening cash is $450,000, the minimum balance is $200,000 and payroll is $180,000 every two weeks. Week 1 starts on Monday, October 5, 2026.

Week 3 carries the quarterly sales tax remittance of $60,000, and week 5 the loan interest of $25,000. Week 6 closes at $124,000 before funding, $76,000 below the minimum. With no funding, week 7 would close at $220,000 and week 8 at $73,000. A revolver draw of $150,000 in week 6 lifts the closing balances to $274,000, $370,000 and $223,000, all above the minimum, which is why weeks 7 and 8 open higher in the table.

The reading: the payroll weeks are the troughs, and the forecast shows the draw is needed three weeks before it happens. The template carries all 13 weeks. Week 11 holds the December 15 federal estimated tax installment, one of the four corporate installment dates, and the lowest week after funding is week 12, at $212,000.

Forecasting receipts from the receivables ledger

Place each open invoice in the week it is likely to be paid, using how that customer has actually paid, not the payment terms. For each customer, the average days late across paid invoices is the gap between due date and paid date. The expected date of an open invoice is its due date plus that average:

=IF(D5="","",D5+F5)

and its week is found against the 13 week start dates on Inputs, with anything overdue in week 1 and anything after week 13 marked "Later":

=IF(G5="","",IF(G5<Inputs!$B$9,1,IF(G5>Inputs!$C$21,"Later",MATCH(G5,Inputs!$B$9:$B$21,1))))

Customer receipts for a week are then one SUMIFS over the AR sheet. This is the per-customer view behind days sales outstanding. A customer who is close to their limit, as in credit limit headroom, is also the one whose receipt is most worth checking by hand.

What is in the template

• Inputs. The Monday of week 1, opening cash (the bank balance that day), minimum cash and the revolver limit. The 13 week dates fill themselves.
• Paid and AR. Paid invoices give each customer's average days late by AVERAGEIFS; open invoices are placed by week as above.
• AP. Open bills with a planned payment date, which defaults to the due date. Choosing which bills to hold is the days payable outstanding decision, made one week at a time.
• Fixed. Dated payroll, rent and other opex, sales tax, estimated tax and loan interest, one row per payment.
• Forecast. The 13 weekly columns. The draw needed to hold the minimum is:

=MAX(0,Inputs!$B$5-H16)

The yellow rows are for the draws and repayments you decide on. Below them, the sheet shows the lowest closing cash, its week, and the first week below the minimum before funding.

• Summary. One row per week, for reading and for the lender's pack.
• Variance. Last week's forecast against actual by line, with accuracy.

The weekly roll and the variance check

Every week: enter the finished week's actuals on Variance, move the Monday on Inputs forward one week, and refresh AR, AP and Fixed from the ledgers. Week 13 is new each time. A 13-week forecast built once and left is a nine-week forecast a month later.

Receipts accuracy is the number to watch:

Accuracy = 1 − |actual − forecast| ÷ actual

In the sample, the week before week 1 forecast $290,000 of receipts and collected $262,000, which is 89.3% accurate, and closing cash came in $30,500 below forecast. Kept week after week, the same measure shows bias, as in how to measure forecast accuracy and bias in Excel.

The check that proves it

1. Week 1 opens at the bank balance. Opening cash on Inputs is the bank balance, and the finished week's actual closing cash on Variance must equal it. Both differences show as 0.
2. The weeks roll. Week 13 closing equals week 1 opening plus all receipts, minus all disbursements, plus draws, minus repayments. In the sample: 450,000 + 4,125,000 − 4,382,000 + 150,000 = 343,000.
3. Nothing is lost. Open receivables equal the receipts placed in weeks 1 to 13 plus those marked "Later": 4,125,000 + 235,000 = 4,360,000. Every Fixed row has a line the forecast reads.

Where it goes wrong

• Receipts from terms. Forecasting each invoice on its due date, not on how the customer pays, makes the forecast optimistic every week.
• The accrual P&L in a cash forecast. Depreciation and accruals are not cash.
• Missing lumpy items. Estimated tax installments, insurance premiums, bonuses and the third biweekly payroll in a month all land inside 13 weeks.
• Not rolling it. Drop the finished week and add a new week 13 every week.
• Monthly blind spots. Payroll on the 25th and receipts on the 30th can make a trough that a monthly view never shows.

When the template stops being enough

The receipts line is only as good as each customer's payment history, and keeping Paid and AR current by hand is the slow part. Covirage's tools compute each customer's average days to pay from your paid-invoice history and, applied to the open invoices in your AR aging, the week each invoice would land in if the customer pays as they have before. That is a computation from your own rows, not a promise of when cash will arrive; the external AI model explains the trough and never does the arithmetic. See FP&A reporting. For the year-end view of where cash went, see the cash flow statement example. For the longer view, see cash flow forecast; for the receivable, inventory and payable days behind the weekly lines, cash conversion cycle and working capital.