Cash Flow Forecasting: How to Build a 13-Week Forecast

Why cash needs its own forecast

Profit forecasts do not show timing. A cash forecast shows when money actually arrives and leaves, so you can see shortfalls before they happen.

A business can be profitable and still miss payroll. Customers pay late. Inventory is bought weeks before it is sold. Taxes, insurance and loan payments land in lumps. A profit and loss statement spreads these over time, but your bank account does not.

A cash forecast puts each item in the week it is expected to hit the account. That is why it works as an early warning system. If week 9 goes negative, you have two months to act.

Read cash flow vs. profit if you want the difference in more detail.

Set up the layout

Use a spreadsheet with weeks as columns and four blocks: opening cash, cash in, cash out, and ending cash. Each week's ending cash becomes the next week's opening cash.

Create thirteen columns, one per week, starting with the current week. Rows:

1. Opening cash balance (from your bank).
2. Cash in: customer collections, deposits, other income, loan proceeds.
3. Cash out: payroll and taxes, rent, supplier payments, loan payments, insurance, owner draws, capital purchases.
4. Net cash change = in minus out.
5. Ending cash balance = opening plus net change.

Add a minimum cash line, such as one month of fixed costs, and highlight any week that falls below it. A ready layout is in our cash flow projection template guide.

Forecast cash in from real invoices and orders

Start with unpaid invoices and their expected payment dates, then add expected new sales converted to cash using your actual payment pattern.

Use your accounts receivable list. For each open invoice, estimate the week it will be paid based on the customer's history, not the due date. Some customers pay on time, others consistently run 20 days late.

For future sales, forecast by week and then shift into collection timing. If 60 percent of customers pay within 15 days and 40 percent within 45 days, apply those splits.

For retail or restaurants with immediate payment, deposits arrive within a few days, minus card processing fees. Be conservative. If a large payment is uncertain, show it a week or two later or leave it out of the base case.

Forecast cash out with a calendar

List every payment by its date: payroll, rent, taxes, suppliers, loans, insurance and one-time items. Do not smooth annual bills into monthly averages.

Pull a calendar of recurring obligations from your bank statements and accounts payable. Pay close attention to:

• Payroll frequency and payroll tax deposits.
• Quarterly estimated taxes, sales tax and other filings.
• Annual or semiannual insurance, licenses and subscriptions.
• Supplier terms, such as net 30 payments.
• Debt payments and how often they are debited, daily, weekly or monthly.

Add a small unexpected-costs line. Be honest about owner draws. If you use daily or weekly debits, convert them to the correct week. See daily payment to monthly equivalent.

A short worked example

A business starting with $30,000 can dip to $4,000 in week 6 and recover after collections, even though its monthly profit is positive.

Illustrative example, in dollars.

If the minimum cash level is $10,000, weeks 4 to 6 breach it. Options include collecting early, delaying a purchase, asking a supplier for terms or arranging a line of credit before the dip.

Run a downside case

Copy the forecast and cut collections by 15 to 20 percent or delay big customer payments by two weeks. See where cash breaks and what you would do.

A single forecast gives false comfort. A downside case shows how fragile the plan is. Change a few assumptions at a time: a major customer pays 30 days late, sales drop 15 percent, a key supplier demands cash on delivery.

Write down the triggers and responses in advance. For example: "If week 8 cash falls below $8,000, pause the equipment order and call the bank." Our guide to stress-testing payments if revenue drops applies the method to debt.

Also test an upside. Rapid growth consumes cash too, because you buy inventory and pay staff before customers pay you.

Maintain it weekly and act on what it shows

Update with actual balances every week, roll the forecast forward one week, and review variances. Fix the cause of recurring misses.

Set a fixed time each week. Replace last week's forecast with actuals, adjust upcoming collections and payments, and add a new week at the end. Note the biggest differences and why. Over a few cycles your estimates will get sharper.

Tools you can pull when a gap appears: faster invoicing, deposits, early-pay discounts, renegotiated supplier terms, and trimmed spending. If the gap is temporary and the business is sound, a business line of credit lets you draw only what you need and repay it. For a larger one-time need, working capital may fit.

ROI Funder considers 500+ FICO, 6+ months in business and $20,000+ monthly revenue, and shows true cost and payback before you sign. Funds can arrive the same business day on approved, complete files. See cash flow management for related habits.