The 13-week cash flow forecast: a practical guide for owner-led businesses

Profitable businesses run out of cash all the time. Customers pay late, a big annual bill lands in the same week as payroll, a loan payment resets, an expansion costs more up front than planned. None of that shows up on a profit and loss statement until it's too late. The tool that catches it early is simple, and most small businesses don't have one: a rolling 13-week cash flow forecast.

Why 13 weeks

Thirteen weeks is one quarter. It's long enough to see trouble coming, with time to act on it: chase receivables, delay a purchase, draw on a credit line, talk to the bank before it's urgent. It's also short enough to forecast with reasonable accuracy, because most of the cash moving in the next three months is already known: payroll dates, rent, loan payments, open invoices, recurring revenue.

Weekly beats monthly. Cash crunches happen inside a month: payroll on the 15th, a big supplier payment on the 20th, customer receipts arriving at the end. A monthly view averages those away.

The layout

One row per kind of cash movement and one column per week, starting with this week:

Closing cash for each week becomes the opening cash for the next. The figures are an example. The row that matters most is the last one, and the week it gets close to your comfort level.

Building it, step by step

1. Start with today's cash. The actual bank balance across your operating accounts, not the balance in the books.
2. List the fixed outflows first. Payroll dates and amounts, rent, loan payments, insurance, software, taxes you know are due. These are the most predictable lines and often the biggest.
3. Forecast receipts realistically. Use open invoices and how long each customer actually takes to pay, not the terms on the invoice. Add recurring revenue you can count on, and be conservative with new sales.
4. Add variable costs. Suppliers, materials and other spending that moves with volume. Last quarter's weekly average is a reasonable start.
5. Put in the one-offs. Annual bills, equipment purchases, owner distributions, a planned hire's start date.
6. Set a floor. Decide the minimum cash balance you want to hold. A common rule of thumb is at least a couple of payrolls. Highlight any week that dips below it.

A spreadsheet is fine. The forecast doesn't need special software; it needs a person who updates it every week.

Keeping it useful

The forecast is only valuable if it's rolling and honest:

• Update it weekly. Replace last week's forecast with actuals, add a new week thirteen, and adjust anything that's changed. Fifteen to thirty minutes once it's set up.
• Compare forecast to actual. If receipts keep coming in lower than forecast, your assumptions are too optimistic. Fix them.
• Write down the decisions. When a week dips below the floor, note what you'll do about it and when: chase a specific invoice, move a purchase, call the bank.

What it tells you

A good 13-week forecast answers the questions owners lose sleep over:

• Can we make payroll every week this quarter, with room to spare?
• Can we afford this hire, this equipment or this expansion now, or should it wait six weeks?
• How much can the owner safely take out?
• Do we need a line of credit, and when, while there's still time to get one?

Banks also tend to respond better to a business that shows them a forecast than to one that calls when cash is already short.

Getting help

A rolling 13-week cash forecast is a standard part of our fractional CFO and controller work, and often the first thing we build for a new client. If cash keeps surprising you, book a free 30-minute call. Pyxis engagements start at $1,500 a month; see how engagements work.