SBA Resources · For Owners · Updated July 2026
The 13-Week Cash Flow Forecast
The single most important tool for not running out of money — and the one thing most new owners learn too late. See the week you go short before it arrives.
A 13-week cash flow forecast is a rolling, week-by-week projection of cash in and out over the next quarter. It exists to answer one question a profit-and-loss statement can't: when will I run short? The trap for anyone who bought a business with a loan is that loan principal drains cash but never shows up as an expense — so you can be profitable on paper and still miss payroll.
Written by Thomas Hartwell, author of the FUNDED series of industry-specific SBA lending guides.
Project Your Next 13 Weeks
Enter typical weekly figures to see your cash trajectory. The downloadable sheet lets you vary every week individually.
Payroll, rent, suppliers, taxes, owner pay — everything except the loan payment.
Cash out, but NOT a P&L expense.
Get the downloadable Excel sheet — free
The full Excel version lets you vary every week, splits your loan principal automatically, and turns red the week you run short — built from the same engine as our deal-analysis kit.
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Why "profitable" businesses miss payroll
Profit is earned; cash is what's in the account today. A profitable business can still run dry when cash is locked in receivables, prepaid inventory, or a tax bill — and, for anyone who financed a purchase, loan principal. Running out of cash is the most-cited reason businesses fail.
You can be profitable every single month and still go broke, because profit and cash answer different questions. A 13-week forecast tracks the one that pays your people: cash.
The principal trap, if you bought with a loan
When you repay a loan, only the interest is a business expense on your P&L. The principal is a cash outflow that never touches the income statement. Acquisition buyers carry large amortizing loans, so a big slice of every payment quietly drains cash while your profit looks fine.
This is why the tool above makes you split the payment. Enter only the interest and your forecast lies to you; enter the principal too and you see the real trajectory — often a slow bleed that turns red a couple of months out, exactly when you'd otherwise be blindsided.
It complements QuickBooks — it doesn't replace it
QuickBooks records what already happened. A 13-week forecast projects what's about to happen to your cash. QuickBooks Online's cash-flow statement is hard to read and its planner is limited, which is why owners and accountants export to a spreadsheet to forecast. Keep QuickBooks as your ledger; use this as your early-warning system.
Feed the forecast from your QuickBooks actuals each week — collections, payroll, the loan payment from your amortization schedule — and roll it forward. Thirteen weeks is the sweet spot: far enough to act, close enough to be accurate.
Frequently Asked Questions
What is a 13-week cash flow forecast?
A 13-week cash flow forecast is a rolling, week-by-week projection of the cash coming into and going out of a business over the next quarter (13 weeks ≈ 90 days). Unlike an annual budget, its weekly cadence catches short-term crunches — like a payroll week that lands on a slow collections week — and shows exactly when the cash balance goes negative, weeks before it happens. It is the standard tool treasury and turnaround professionals use to manage cash.
Why can a profitable business still run out of cash?
Profit and cash are different. Under accrual accounting, profit is recorded when a sale is earned, but the cash may be tied up in receivables, prepaid inventory, or a looming tax payment. The biggest hidden drain for anyone who bought a business with a loan is loan principal: the principal portion of every payment reduces your cash but never appears as an expense on the profit-and-loss statement. So you can show a profit every month and still be unable to make payroll.
Does a 13-week forecast replace QuickBooks?
No — it complements it. QuickBooks records what already happened; a 13-week forecast projects what is about to happen to your cash. QuickBooks Online's built-in cash-flow statement uses the indirect method that is hard to read, and its cash-flow planner has limited horizon and flexibility, which is why owners and accountants export to a spreadsheet to forecast. Use QuickBooks as your ledger and the 13-week forecast as your early-warning system.
How do I separate the principal and interest in my loan payment?
Your lender's amortization schedule shows the split for every payment. Early in an SBA loan most of the payment is interest; over time more goes to principal. For cash planning, both come out of your bank account, but only the interest is a business expense. Enter them separately so your forecast reflects the true cash outflow, not just the expense your P&L shows.