How to build a 13-week cash flow forecast

What to take away

Start from a reconciled bank balance and date every receipt and payment in the week cash actually moves.
Enter customer money when you expect to be paid, not when you invoice, and test a slower-collection case.
Compare forecast with actual every week, then adjust the next weeks rather than starting over.

What a 13-week forecast is for

Thirteen weeks is one quarter. It is long enough to see the payroll runs, rent payments, tax remittances and supplier bills that are coming, and short enough that you can estimate most of them with some confidence. BDC offers a free spreadsheet template with a 13-week view for short-term needs and a 12-month view for the longer picture, so you can use the same layout for the short and the longer view.

This is a different tool from the annual budget and from the profit report. If your question is why profit and cash have drifted apart, start with why a profitable business can still run short of cash. If your question is what you will have in the bank in week seven, this is the page.

Set up the grid

Open a spreadsheet and put the thirteen week-ending dates across the top. Down the left side, create three blocks: cash coming in, cash going out, and the balance. Under cash in, list customer receipts by source, plus anything else such as loan advances or owner contributions. Under cash out, list payroll, rent, suppliers, loan payments, tax and sales tax remittances, insurance, software and owner draws.

Keep one row per commitment that has its own timing. Lumping everything into a row called expenses hides the weeks that matter. Add four lines at the bottom: opening balance, total in, total out and closing balance, where each week’s closing balance becomes the next week’s opening balance.

Start from a reconciled balance

Week one’s opening balance should be the bank balance after you have reconciled it, meaning you have matched the books to the statement and accounted for cheques and payments that have not cleared. If you start from the online balance alone, an uncleared payment can sit outside the forecast and show up as a surprise.

If you have several accounts, forecast the total you can actually use. Money set aside for sales tax, payroll remittances or a customer deposit is committed, so treat it as a payment in the week it is due, not as spare cash.

Forecast receipts by when you expect to be paid

The most common error is entering a sale in the week you invoice. BDC’s guidance on projections is direct on this point: record a sale as cash only when you expect to be paid, and do not assume sales equal cash in the bank right away. Go through your open invoices one by one and place each in the week you realistically expect it to clear, using the customer’s actual payment history rather than the terms printed on the invoice.

For sales you have not yet invoiced, estimate the work, then apply your usual lag between invoicing and payment. Mark any single large receipt, because one late payer can decide the whole forecast. Our article on how to collect receivables faster covers the follow-up side.

Forecast payments by due date

Work from your recurring commitments first: payroll and the related source deductions, rent, loan instalments, insurance and subscriptions. Then add the irregular ones that you already know about, such as an equipment purchase, a quarterly sales tax remittance, a corporate or personal tax instalment, or a year-end bonus. Check the actual due dates on your filing calendar and notices rather than recalling them.

Put owner pay in the forecast too. Salary, dividends or draws are real cash movements, and leaving them out is how a forecast looks healthy until the week you pay yourself. If you collect GST/HST, remember that it is not spending money; see why GST/HST collected is not spending money.

Test a slower case and keep a cushion

One forecast gives you a single story. BDC suggests building optimistic and pessimistic versions so you can see how different outcomes affect your finances. For a 13-week forecast, the simplest second case is to push your largest customer receipts back by two or three weeks and see whether the balance goes negative, and in which week.

BDC also notes that many entrepreneurs aim for enough cash for 90 days of operations, which can include cash in the bank and room on a line of credit. Treat that as a reference point to discuss, not a rule; the right cushion depends on how predictable your receipts are. Decide in advance what you would do if the pessimistic case happens, such as chasing a receivable, delaying a purchase or talking to your lender early.

An illustrative example

These numbers are illustrative and round. A small business opens week one with $20,000 in the bank. It expects $15,000 of customer receipts in each of weeks two, six and ten, and pays $7,000 of payroll in each of weeks two, four, six, eight, ten and twelve. Rent of $3,000 is paid in weeks one, five, nine and thirteen, and a $6,000 supplier bill falls due in week five.

On those dates the balance never goes below zero, but it ends week thirteen at only $5,000, which leaves little room for an unexpected bill. Now test a slower case: if the week-six receipt arrives in week nine instead, the balance falls to negative $5,000 in week eight, just before the money arrives. That gap is the reason to build the forecast, because it shows weeks ahead of time that you would need to chase the payment, delay a purchase or arrange credit.

Update it every week

A forecast is useful only while it is current. Once a week, replace the finished week’s estimates with actual figures, look at where you were wrong, and roll the grid forward so there are always thirteen weeks ahead. BDC recommends comparing projections with actual results to spot shortfalls early and adjust.

Pay attention to the pattern in your errors. If receipts are always a week late, change the assumption rather than the single invoice. When you meet your accountant, bring the forecast, the aged receivables list and your upcoming tax and payroll dates, and ask which commitments you may have missed. Sora’s cash runway tool gives a simplified estimate, and the 13-week grid gives the detail behind it.

Sources & editorial notes

Sources checked October 24, 2026. The examples are illustrative and provide general information. Discuss how the guidance applies to your circumstances with your accountant.

Rules and guidance can change. Use the current official source and confirm the treatment for your facts. To flag an error, contact Sora.