A profitable business can still face a bad cash week. An invoice may count toward revenue long before the customer pays, while payroll and rent arrive on fixed dates. A 13-week cash-flow forecast is a practical way to see those timing problems before they become urgent. It is a planning worksheet, not a prediction or a substitute for your financial statements.
The basic calculation is straightforward: opening available cash + expected cash received − expected cash paid = closing available cash. Government guidance on cash-flow forecasting uses this same opening-balance, inflow, outflow, and closing-balance structure. The weekly format below is a suggested management approach; the 13-week horizon is not a legal requirement or a guarantee that every risk will be captured.
Start with money you can actually use
Choose one starting date and reconcile the opening figure to your bank records. Exclude restricted funds and money held for someone else. Show committed payments clearly rather than treating every dollar on a banking dashboard as freely spendable. An undrawn credit line belongs in a separate financing section, not in your opening bank balance.
Use 13 columns, one for each week. Under each column, give receipts, operating payments, financing movements, and closing cash their own rows. Keep the first version simple enough that you can update it in one sitting. A detailed model nobody maintains is less useful than a short model with current assumptions.
Forecast receipts by collection date, not invoice date
Take each meaningful outstanding invoice and write down when you reasonably expect the money to arrive. A promised payment, a disputed invoice, and a proposal that has not been accepted should not receive the same confidence level. Put the customer, amount, expected date, and reason for the estimate in a notes column.
For card sales or marketplace revenue, model the cash settlement you expect to receive. Avoid counting gross sales once and the same processor payout again. Treat refunds, fees, reserves, and settlement delays consistently with your actual statements. When timing is uncertain, build a later-payment scenario rather than quietly assuming the best.
Make the payment calendar specific
List obligations in the week they are expected to leave the account. Do not spread a large quarterly payment evenly across three months if the money must leave all at once. Include owner distributions and debt principal payments even when their accounting treatment differs from an ordinary operating expense.
- People: payroll, related payments, and agreed contractor invoices.
- Operations: rent, utilities, subscriptions, insurance, inventory, and supplier payments.
- Calendar items: taxes, renewals, deposits, equipment purchases, and seasonal commitments.
- Financing: borrowing, interest, principal repayments, and owner contributions or withdrawals.
Your records should support these entries. The IRS recordkeeping guidance explains why businesses need records of income, expenses, and supporting documents. This forecast does not determine what is deductible or when a tax payment is legally due; obtain that information from your accountant and the applicable agency.
A worked example: the problem is week two
Hypothetical example—not a client result: a small service business begins with $30,000 of available cash. In week one it expects $18,000 of receipts and $22,000 of payments, leaving $26,000. In week two it expects $12,000 of receipts and $29,000 of payments, leaving $9,000. In week three it expects $28,000 of receipts and $20,000 of payments, leaving $17,000.
The three-week ending balance looks manageable, but it hides a dip. Suppose management has chosen a $15,000 planning floor based on its obligations and risk tolerance. Week two falls $6,000 below that floor. That is a signal to investigate now—not proof the business needs exactly $6,000 of borrowing. The floor is an assumption in this example, not a recommended minimum for every business.
Now stress-test a $10,000 customer payment expected in week two. If it slips into week four and nothing else changes, week two closes at negative $1,000. The business has learned something actionable: the collection date matters more than the attractive week-three total. Confirm the payment, evaluate discretionary spending, and discuss any financing or revised terms before an obligation is missed.
Use three scenarios, not false precision
Keep a base case, a slower-collections case, and a case with a plausible unexpected payment. Change a small number of assumptions so you can explain why the balances move. A downside scenario should identify decisions: which commitment can be delayed by agreement, which purchase can wait, and who owns the next customer follow-up. Never assume a tax, wage, or contractual obligation can simply be postponed.
Pay special attention to the lowest projected balance, the week it occurs, and the largest uncertain receipt. A forecast that depends on one unconfirmed sale deserves a different response from one supported by a broad set of reliable collections.
Turn the forecast into a weekly meeting
Replace last week’s estimates with actual receipts and payments. Record why material differences happened: a late customer, a missing invoice, an expense omitted from the model, or simply the wrong timing assumption. Then add a new thirteenth week. Keep the earlier version so you can distinguish a genuinely improving position from repeatedly moving an optimistic receipt forward.
End the review with three assignments: the most important collection action, the largest upcoming payment to verify, and the spending decision that depends on available cash. Give each one an owner and a date. The forecast becomes useful when it changes a decision, not when it produces a colorful spreadsheet.
Your next step
Build the first four weeks using actual bank balances, open invoices, and scheduled payments. Extend to 13 weeks only after the opening section makes sense. For background, read what cash flow means and ways to approach cash-flow problems. Use an appropriately qualified adviser when decisions involve borrowing, solvency, tax, or other legal obligations.
Educational information, not individualized financial, accounting, or legal advice. All numerical examples above are hypothetical. Prepared with AI assistance; the linked sources were checked during preparation on September 27, 2026.