How to Build a 13-Week Cash Flow Forecast for a Business You Just Bought

A 13-week cash flow forecast for a business you just bought is one sheet that shows, for each of the next 13 weeks, opening cash, the receipts you expect, the payments you are committed to and closing cash, set against a minimum you choose. Build it from the bank balance in your first week as owner, put every payment you cannot move in the week it clears, and update it every week.

Thirteen weeks is 91 days. The JPMorgan Chase Institute's September 2016 report Cash is King studied 597,000 small businesses from February to October 2015. The median business held 27 cash buffer days, meaning it could cover 27 days of outflows from its balance if receipts stopped, and 25 percent held fewer than 13 days. A buyer who now owes a lender or the seller every month has no reason to assume a thicker cushion until the sheet shows one.

What goes into a 13-week cash flow forecast?

A 13-week cash flow forecast holds dated cash movements and nothing else: money you expect to land in the account and money you are committed to pay out, each placed in the week it will clear the bank. Depreciation, accrued expenses and invoices you have sent but not collected stay off the sheet until cash moves.

That is the difference from the income statement the seller showed you. A sale invoiced in week 2 on 45 day terms is revenue in week 2 and cash in week 9. The guide to owning the business you bought explains why the weekly view comes first: the loan payment, the payroll and the supplier terms all run on cycles shorter than a month.

The sheet has the same lines every week. Copy these into a spreadsheet, one row each, with the weeks running across.

A worked 13-week forecast

The example below is fictional. It describes an invented business that opens with $40,000 in the bank and sets its minimum at $25,000, and no figure in it is a benchmark or a real company. It shows the sheet turned on its side, one row per week, which is easier to read on a phone than 13 columns.

Three formulas hold the sheet together. Net change is cash in minus cash out. Closing cash is opening cash plus net change. Next week's opening cash is this week's closing cash.

In the example, week 6 is the collision: payroll, the loan payment and an insurance renewal clear in the same 7 days, and cash drops by $17,700. Week 8 is the real problem. Payroll clears a week before the largest customer's $15,000 payment arrives, and closing cash falls to $21,800 against a $25,000 minimum. A monthly income statement for the same quarter would show neither week.

How do you fill it in during the first week of ownership?

Fill the sheet from documents in a fixed order: the bank balance first, the payments you cannot move second, receipts last. Estimates go in only after every dated commitment has a week.

1. Opening cash. Use the bank balance on the morning you start, less any checks and payments that have not cleared. IRS Publication 583, revised December 2024, says a business should reconcile its checking account each month, and that reconciling verifies how much money is in the account. The sheet is only as good as that starting number.
2. Payroll. Take the dates and gross cost from the payroll provider's last 3 runs. Put your own salary in this line, at the market rate for the job you do.
3. Rent, debt service and dated bills. Read the lease, the loan note, the seller note and the insurance schedules for due dates and amounts. Enter each one in the week it drafts.
4. Vendors. List the suppliers paid in the last 90 days from the bank statements, with their terms.
5. Taxes. Ask your accountant which deposits and filings fall inside the 13 weeks, and enter the dates and amounts.
6. Receipts. Split them by how they arrive. Card and cash sales land within days. Invoiced customers pay on their own habits, so use the dates they have actually paid on.
7. Owner draw. Leave it at zero until closing cash stays above your minimum in all 13 weeks.

The minimum cash line is your decision. One way to start is the cost of one payroll plus one loan payment, rounded up. In the example, one $16,000 payroll and one loan and note payment come to $22,200, so the minimum is set at $25,000. If you ran the revenue reconciliation worksheet before closing, the receipts lines start from deposits you have already traced.

What should a new owner do when a week falls below the minimum?

A week below the minimum is a timing problem you can see early, so change the timing of a payment or a receipt before you look for new money. In the example, the shortfall in week 8 shows up in week 1, which leaves seven weeks to act.

Start with the items you control. Ask the late-paying customer for a deposit or shorter terms on the next order. Ask a supplier to move one invoice by a week. Hold a purchase that can wait. Then rerun the sheet and see whether the gap closes.

Borrowing to cover operating costs is common. In the Federal Reserve Banks' 2026 Report on Employer Firms, drawn from the 2025 Small Business Credit Survey of 6,525 employer firms, 60 percent of firms had applied for financing in the prior 12 months, and meeting operating expenses was the most common reason, cited by 56 percent. If a line of credit is part of your answer, talk to the lender while the shortfall is still a forecast.

The sheet also checks a number from before closing. The debt coverage check asks whether a year of earnings covers a year of payments. The weekly sheet asks whether the money is in the account on the day the payment drafts. A business can pass the first test and still miss the second in week 8.

How do you keep the forecast honest after week 1?

Keep the forecast honest by recording actual closing cash every week and writing the variance beside what you forecast 7 days earlier. If week 1 in the example had closed at $43,600 against the $45,000 forecast, the gap between them is the variance, and the line that caused it is the one to check first.

Pick one day and do it in the same order each time. Enter the actual figures, write one line explaining any variance worth explaining, correct the weeks ahead, and add a new week 13 so the sheet always looks 91 days out. The owner responsibilities guide keeps cash and the next 13 weeks of payments on the owner's weekly list for the same reason.

After 12 weeks of actual figures you can say how far off the forecast tends to run. Whatever that margin turns out to be, the minimum line needs at least that much room above your worst week. If you cannot state a margin, the variance column shows which line keeps surprising you.

The free lesson on the first ninety days after you own it covers what else to read before you change anything. This worksheet is a working aid. It does not replace advice from your accountant, lender or attorney.