A 13-Week Cash Flow Forecast: See a Cash Shortage Before It Happens

Summary: A profitable business can still struggle to pay bills on time. A rolling 13-week cash forecast turns upcoming deposits and payments into a weekly view of available cash, giving owners time to act before a shortage develops.

Your income statement may show a strong month while your bank balance tells a different story. Perhaps a major customer has 45-day payment terms, payroll is due Friday, and an annual insurance premium hits next week. The challenge is not necessarily poor sales. It is the timing of cash.

A 13-week cash flow forecast is a simple way to see that timing. It is a management planning tool—not a replacement for your bookkeeping records, bank reconciliation, or formal financial statements.

What belongs in the forecast?

Set up a spreadsheet with one column for each of the next 13 weeks and rows for five essential items:

1. Beginning available cash: the amount you can actually spend at the start of the week, excluding restricted funds or balances reserved for obligations you cannot use for operations.
2. Expected cash receipts: customer payments, deposits, and other funds expected to clear that week. Use realistic collection dates, not invoice dates.
3. Expected cash payments: payroll, rent, supplier invoices, taxes, loan payments, subscriptions, insurance, and planned equipment purchases.
4. Net cash change: receipts minus payments.
5. Ending available cash: beginning cash plus net cash change. This becomes the next week’s opening balance.

A simple example

Suppose you start Monday with $12,000 available. You expect $5,000 in customer collections and $9,000 in payments during the week. Your forecast ending cash is $8,000 ($12,000 + $5,000 − $9,000).

Now assume next week’s payroll and other bills total $11,000 but collections are not expected until the following week. The forecast reveals the potential gap early enough to follow up on overdue invoices, adjust discretionary purchases, or discuss a financing option with your lender. It does not guarantee those actions will solve the gap, but it makes the risk visible.

Build it in five practical steps

1. Start with your actual bank position. Reconcile the bank balance and account for outstanding checks, pending card settlements, and any cash that is not available for spending.
2. List customer receipts by likely arrival date. Review open invoices and customers’ payment histories. Separate confirmed payments from optimistic estimates.
3. List every significant payment. Include irregular items such as quarterly estimated taxes, annual renewals, bonuses, and equipment deposits. Do not treat sales tax collected on behalf of a government as free operating cash.
4. Set a minimum cash cushion. Choose a working threshold based on payroll, essential bills, and your risk tolerance. If a projected ending balance falls below it, flag the week.
5. Refresh the forecast every week. Replace estimates with actual transactions, explain material differences, and add a new thirteenth week.

Three mistakes to avoid

Confusing profit with cash. Revenue recognized today may not arrive in the bank until weeks later. Assuming every invoice will be paid on time. Build collection assumptions from evidence and consider a slower-payment scenario. Ignoring one-time payments. Tax deposits, renewals, and equipment purchases often create the sharpest dips.

What to review each Friday

Ask: What changed since last week? Which customer payments slipped? What is our lowest projected cash balance in the next 13 weeks? Which commitments can we make safely? A 15-minute review with an updated forecast can be more useful than a beautifully formatted spreadsheet no one maintains.

Bottom line: Bookkeeping records what happened. A rolling cash forecast helps you decide what to do next. For businesses with uneven collections or seasonal expenses, that forward view can be especially valuable.

Sources and further reading

• FDIC and SBA — Money Smart for Small Business, including the Managing Cash Flow module.
• SBA/SCORE — Develop Your Cash Flow Projection (October 14, 2026 workshop description).
• SBA/SCORE — Creating Realistic Financial Projections for Your Small Business (October 21, 2026 workshop description).

3A Bookkeeping Services | A service of 3A IT Consulting, LLC. Educational information; consult your accountant or tax adviser for decisions specific to your business.