Guide

How to make a 13-week cash flow forecast

A 13-week cash flow forecast shows how much cash you'll have at the end of every week for the next three months. Here's how to build one step by step, with a worked example, and how to get one from your QuickBooks Online books in a few minutes.

Updated October 13, 2026

What a 13-week cash flow forecast is

It's a week-by-week plan of the cash coming in and going out of your business. Each week starts with the cash you have, adds what you expect to receive, takes away what you expect to pay, and ends with the cash left over. That becomes the next week's starting cash.

It's about cash, not profit. A profitable business can still run short: customers pay late, a quarterly tax bill lands in the same week as payroll, or a big supplier order is paid before the sales come in. Your profit and loss report won't show you that week. A cash forecast will.

Why 13 weeks, and why weekly

• 13 weeks is one quarter. That's far enough ahead to see a crunch coming while there's still time to act, and near enough that weekly figures are still believable.
• Weekly, not monthly. A month can look fine in total and still hide a week where payroll goes out before customers pay.
• It rolls. Each week, the week that's over drops off and a new week 13 is added, so you always see a full quarter ahead.
• Lenders know it. Banks, lenders and advisers often ask for cash flow in this format.

What goes into it

Opening cash

The money in your bank accounts at the start of the week.

Cash in

Customer payments on invoices you've sent, new sales you'll collect, and any other money in, like a loan or an owner's contribution.

Cash out

Payroll and payroll taxes, rent, suppliers, loan repayments, card payments, taxes, insurance, subscriptions and owner draws.

Net cash flow

Cash in minus cash out, for the week.

Closing cash

Opening cash plus net cash flow. It's next week's opening cash.

Safety line

The least cash you want to hold. Weeks below it are the ones to deal with now.

How to build one, step by step

1. 1

   Gather your numbers

   You need:

   • The cash in your bank accounts today: the real balance, not what your books say if they're behind.
   • Your unpaid customer invoices (the accounts receivable aging report), with due dates.
   • Your unpaid bills (the accounts payable aging report).
   • Payroll dates and amounts, including payroll taxes.
   • Regular payments: rent, loan repayments, card payments, insurance, software.
   • Tax due dates: sales tax, estimated income tax.
   • The last 12 months of transactions, so you know what a normal week looks like.
2. 2

   Set up 13 weekly columns

   Pick the day your week ends (Friday works well) and label each column with that date. The rows, top to bottom: opening cash, each line of cash in, total in, each line of cash out, total out, net cash flow, closing cash.

3. 3

   Forecast cash in

   Start with invoices you've already sent. Put each one in the week you expect to be paid, not the week it's due. If a customer usually pays three weeks after invoicing, plan for three weeks.

   Then add new sales you expect to collect within the 13 weeks. Your history is the best guide: what do you usually collect in a typical week, and is there a busy or quiet season coming? Be cautious. It's better to be pleasantly surprised.

4. 4

   Forecast cash out

   Fixed dates first: payroll on its actual pay dates, rent, loan repayments, card payments. Then your unpaid bills, in the week you'll pay them. Then everyday spending, from your recent average.

   Then look for the lumpy ones that are easy to forget: quarterly sales tax or estimated tax, annual insurance, bonuses, equipment.

5. 5

   Keep one-offs out of the trend

   If last year had a one-time purchase (a truck, a legal bill, a big repair), don't let it inflate your idea of normal spending, or your forecast will expect it again. If you know a one-off is coming, put it in its exact week.

6. 6

   Roll it forward

   Week 1's closing cash is week 2's opening cash, and so on to week 13. Now you can see your lowest week, and when it comes.

7. 7

   Draw a safety line

   Decide the least cash you want to hold. A simple rule: each week's expected spending plus a buffer. About a month of your average spending is a sensible buffer to start with. Flag any week where closing cash falls below the line.

8. 8

   Act on it, then update it every week

   A forecast is only useful if it changes what you do (see what to do when a week looks tight). Once a week, drop the week that's over, add a new week 13, and compare last week's forecast with what actually happened. That comparison is how your forecasts get better.

A worked example

Here are the first four weeks for an illustrative landscaping business. It starts with $48,200 in the bank, pays staff every two weeks, and holds a buffer of $10,000. The safety line each week is that week's cash out plus the buffer.

Swipe the table sideways to see all four weeks.

The week ending Oct 30 closes at $30,000. That week's cash out is $21,300 (payroll and the quarterly sales tax land together), so the safety line is $31,300. Nothing bounces, but the business is $1,300 below where the owner wants to be. Seeing it weeks ahead, they can chase the slowest invoices, ask a supplier to wait a week, or hold off on a purchase.

What to do when a week looks tight

• Chase late payers first, starting with the biggest invoices from customers who usually pay slowest.
• Ask for deposits or progress payments on large jobs.
• Talk to suppliers before a payment is due, not after. Many will agree to a short delay.
• Time big purchases for after the tight week.
• Arrange a credit line before you need it. It's easier to get while your cash looks healthy.
• Pause spending that can wait.

Common mistakes

• Forecasting profit instead of cash. Use the date money moves, not the date of the invoice or bill.
• Assuming customers pay on time. Use how they actually pay.
• Forgetting the irregular payments. Quarterly taxes, annual insurance, bonuses.
• Letting a one-off repeat. One big purchase last year isn't a monthly cost.
• Starting from the wrong balance. If your books aren't reconciled, start from the bank.
• Building it once. A forecast you don't update stops being useful within a few weeks.

Do it in a spreadsheet, or let your books do it

A spreadsheet gives you full control, but expect a few hours to set one up and time every week to keep it current.

If you use QuickBooks Online, RightTick builds the forecast for you, free. Export one report, your General Ledger for the last 12 months, and drop the CSV in, or connect QuickBooks and skip the export. A forecasting engine works from your own books: your regular income and spending, how quickly each customer usually pays, and the invoices and bills still open. You confirm your cash today and choose a buffer. You see all 13 weeks, with tight weeks flagged and what to do first, and an Excel workbook with live formulas to keep. If you upload, your ledger stays in your browser and there's no signup; if you connect, you get a free account and a forecast you refresh from QuickBooks in one click.

Questions