A thirteen-week cash flow forecast answers one question better than any other financial report: will we have enough cash each week for the next quarter? Monthly budgets and profit-and-loss statements cannot answer it, because they hide timing. A profitable month can still contain a week where payroll, a supplier payment, and a slow customer collide.
This guide walks through building a forecast you can trust and keeping it useful.
1. Start from the bank, not the books
Week one opens with your actual cash balance today, taken from the bank, not the balance sheet. Book balances include deposits in transit and checks that have not cleared, which makes them misleading for a weekly view. If you have several accounts, combine the ones that can actually fund operations.
2. Forecast receipts customer by customer
Receipts are the hardest line to forecast and the most important. Start from your open receivables, then assign each invoice to the week you realistically expect payment. Use how each customer actually pays, not the due date on the invoice. A customer on 30-day terms who reliably pays in 45 days should be forecast at 45.
Add expected new billings that will be collected inside the thirteen weeks. Treat special receipts on their own lines:
- Retainage on construction jobs, which often arrives months after the work.
- Deposits and advance payments, such as association dues or event registrations.
- Seasonal sales, such as grain or livestock sales on a farm.
3. Schedule payments on their real dates
List outflows on the dates they will actually leave the bank:
- Payroll on each pay date, including employer taxes and benefits.
- Supplier and materials payments based on your payables and payment habits.
- Rent, utilities, insurance, and loan payments.
- Estimated tax payments and sales tax remittances.
- One-time items such as equipment purchases, distributions, or annual renewals.
If you do not know an amount yet, leave it visibly blank and flag it. Entering zero makes the forecast look better than reality.
4. Calculate the weekly balance and set a floor
For each week, opening cash plus receipts minus payments gives closing cash, which becomes the next week’s opening cash. Then set a minimum balance you are not willing to go below, such as two weeks of payroll. Highlight any week that falls under it.
5. Update it every week
The forecast is only reliable if it is maintained. Each week:
- Replace last week’s forecast with what actually happened.
- Note why the actuals differed, for example a customer paid late or a bill arrived early.
- Roll the forecast forward one week so it always looks thirteen weeks ahead.
- Look at the lowest week and decide whether to act now.
Comparing forecast with actual each week is what improves your assumptions. After a month or two, you will know which customers to trust and which lines need padding.
6. Act early
The value of the forecast is time. With several weeks of warning, you have options. You can push collections, ask a large customer for a progress payment, delay a discretionary purchase, adjust a hiring start date, or arrange a draw on a line of credit before you need it. Lenders respond much better to a planned request backed by a forecast than to an emergency call.
Keep it separate from the budget
A thirteen-week forecast is not a budget. The budget records the plan management adopted for the year, and the forecast records when cash will actually move. Keep them separate, so you can see both how you are performing against plan and whether you can make payroll in week seven. Our comparison of budgets and forecasts explains why.
Tools
A spreadsheet works well to start. Download our 13-week template or try the cash runway calculator. As the forecast becomes part of monthly management, PursuitBid builds the thirteen-week outlook from your imported records, keeps timing assumptions explicit, and flags missing inputs instead of treating them as zero.
Written by the Syntonyl team. This article is general information, not legal, tax, or financial advice.