Why a 13-week view is different from runway and projections
Most founders already have two finance tools. A three-year model shows where the business could go and what it needs to raise; our guide to startup financial projections covers it. A runway figure divides cash by average monthly burn to show roughly how long the company can operate; see burn rate and runway. Both are useful and both hide timing.
Runway uses averages. A company with twelve months of runway can still miss payroll in week seven if a large customer pays late in the same fortnight that annual software renewals and a tax payment fall due. A 13-week cash forecast looks at that timing directly. It lists expected cash receipts and payments week by week for the next quarter, based on actual invoices, contracts and bills, and shows the lowest point cash will reach.
Thirteen weeks is a common horizon because it covers a full quarter, is short enough to forecast from known items rather than assumptions, and long enough to take action, such as chasing a receivable, delaying a hire or arranging working capital, before a problem arrives.
Forecast cash, not revenue or profit
The single rule that makes this tool work is to record money when it actually enters or leaves the bank account, not when it is earned or billed. Accounting statements, prepared on an accrual basis, record revenue when it is earned and expenses when they are incurred. A cash flow statement, as described in the accounting standards on cash flow statements, reconciles that to actual cash movement. Your 13-week forecast is a forward-looking version of the cash view.
In practice, that means an invoice raised on 1 October with 45-day terms goes into the forecast in the week you realistically expect payment, which may be later than the due date if that customer usually pays late. A vendor bill due on the 10th goes into the week you plan to pay it. GST collected on your invoices arrives with the customer's payment, and GST payable leaves on its due date. Tax deducted at source by customers reduces the cash you receive against an invoice.
Build the receipts side from real evidence
Start with the customer ledger. For each open invoice, record the amount you expect to receive in cash, net of any TDS the customer will deduct, and the week you expect to receive it. Base the week on each customer's payment history rather than the contract date. Our guide to startup accounts receivable explains how to age invoices and track disputes, which feeds directly into this step.
Then add invoices you will raise during the thirteen weeks, but only where there is a signed contract, a purchase order or a clear billing schedule. Place them in the week you expect cash, not the week you invoice. Add other known inflows such as committed grant disbursements with dates, interest, or refunds. Do not include investment that has not been received. A signed term sheet is not cash, and even a signed agreement may have conditions to meet before money arrives.
Finally, mark each receipt as committed, likely or uncertain. This makes it easy to run a scenario without the uncertain items.
Build the payments side, including the lumpy items
Payments are usually easier to forecast because the company controls them, but founders often miss irregular items. List:
- Salaries and contractor payments on their actual dates.
- Statutory payments on their due dates, such as GST, TDS deposited on payments you make, and any provident fund contributions that apply to you. Take dates from official calendars and your chartered accountant.
- Rent, utilities and regular vendor bills.
- Annual or quarterly items: software renewals, insurance, audit fees, compliance filings.
- Loan or interest repayments.
- Planned one-off spending: equipment, deposits, travel for a key deal.
Review the last six months of bank statements to catch recurring payments you forgot. That exercise alone often finds subscriptions nobody uses.
Set a minimum cash buffer
Decide in advance the lowest cash balance you are willing to reach, and treat any week that falls below it as a problem to solve now. The right buffer depends on the business. A common starting point is enough to cover one payroll plus statutory payments, because those are the payments with the most serious consequences if missed. A business with a single dominant customer may want a larger buffer than one with many small customers.
Write the buffer down and agree it with co-founders and, if relevant, the board. The point is to remove debate when the forecast shows a breach: the conversation moves straight to what action to take.
Worked example: a quarter for a Bengaluru B2B startup
This example is hypothetical. A B2B software company has ₹48,00,000 in the bank at the start of the quarter and a minimum cash buffer of ₹30,00,000. The forecast is grouped into three blocks for readability; in the real spreadsheet each week has its own column.
| ₹ lakh | Weeks 1–4 | Weeks 5–8 | Weeks 9–13 |
|---|---|---|---|
| Opening cash | 48.0 | 41.0 | 30.0 |
| Customer receipts (net of TDS) | 14.0 | 9.0 | 22.0 |
| Payroll | (12.0) | (12.0) | (12.0) |
| Vendors and software | (5.0) | (4.0) | (6.0) |
| GST and TDS payments | (2.0) | (2.0) | (3.0) |
| Rent and other | (2.0) | (2.0) | (2.0) |
| Net cash flow | (7.0) | (11.0) | (1.0) |
| Closing cash | 41.0 | 30.0 | 29.0 |
Check the arithmetic: in weeks 1–4, payments total 12 + 5 + 2 + 2 = ₹21 lakh against ₹14 lakh received, a net outflow of ₹7 lakh, so cash falls from ₹48 lakh to ₹41 lakh. Weeks 5–8 pay ₹20 lakh against ₹9 lakh received, falling to ₹30 lakh. Weeks 9–13 pay ₹23 lakh against ₹22 lakh received, ending at ₹29 lakh.
On this base case, cash touches the ₹30 lakh buffer at the end of week 8 and slips below it by the end of the quarter. The average monthly burn looks modest, so a runway calculation alone would not raise an alarm.
Now run one scenario. The ₹22 lakh of receipts in weeks 9–13 includes ₹10 lakh from the largest customer, expected in week 11. That customer has paid about a month late twice this year. If the payment moves to week 16, closing cash at week 13 falls to ₹19 lakh, ₹11 lakh below the buffer.
The founders now have eight weeks to act, and several options:
- Start collection follow-up on the ₹10 lakh invoice now, with the account owner confirming the approval path.
- Ask two customers on annual contracts whether they would prepay for a small discount.
- Move a planned ₹3 lakh software renewal to monthly billing.
- Delay one planned hire by a month.
- Explore working capital options, such as invoice discounting where eligible, early, while there is time to compare terms.
None of these is dramatic. They are possible because the forecast showed the problem two months ahead.
Run it every week
A 13-week forecast is only useful if it rolls forward. Once a week, at the same time:
- Replace last week's forecast with actual bank figures.
- Compare actual receipts and payments with what you forecast, and note the reason for any large gap.
- Add a new week at the end so the horizon stays at thirteen weeks.
- Update receipt timings based on the latest customer conversations.
- Check the lowest projected balance against the buffer and agree actions with owners and dates.
Over time, the variance notes teach you which customers pay late, which costs creep up, and how reliable your forecasting is. That record is also useful when investors ask about cash management during due diligence.
Who owns the forecast and who sees it
Give the forecast one owner. In an early company this is often the founder responsible for finance or a part-time finance lead, supported by an external accountant. The owner does not need to know every number personally, but must collect inputs from the people who do: sales for expected customer payments, operations for vendor commitments, and the accountant for statutory dates.
Share a short summary with co-founders every week: opening cash, lowest projected balance, the week it occurs, and any breach of the buffer with proposed actions. Share it with the board or lead investors monthly, or sooner if the buffer is at risk. Investors generally react better to an early, specific warning with a plan than to a surprise request for a bridge round. Keeping the summary in the same format every time makes changes easy to spot and builds trust in the numbers.
Common mistakes
- Using invoice dates instead of expected payment dates.
- Forgetting TDS deducted by customers, which reduces cash received.
- Counting a signed term sheet or an announced grant as cash.
- Leaving out annual and quarterly payments.
- Building the forecast once for a board meeting and never updating it.
- Keeping it in the founder's head rather than a shared sheet with a clear owner.
Founder cash forecast checklist
- Open a sheet with thirteen weekly columns and opening cash from the bank.
- List every open invoice with expected receipt week, net of TDS.
- Add future billing only where contracts or purchase orders exist.
- List all payments, including statutory and annual items, on their actual dates.
- Set and write down a minimum cash buffer.
- Mark receipts as committed, likely or uncertain and run a downside scenario.
- Review weekly, record variances and roll the horizon forward.
- Agree specific actions, owners and dates whenever the buffer is breached.
Take the next step
If you are preparing to raise and want your financial story in order, you can apply as a founder to RaiseMoney. Applying does not guarantee introductions or investment.
Educational disclaimer
This article is general education, not accounting, tax or financial advice. Statutory due dates and obligations depend on your entity and facts. Consult a qualified chartered accountant.
Sources
Sources reviewed 24 September 2026.
Frequently asked questions
What is a 13-week cash flow forecast?
A week-by-week list of expected cash receipts and payments for the next quarter, based on actual invoices, contracts and bills, showing the lowest point cash will reach.
How is it different from runway?
Runway divides cash by average burn. A 13-week forecast shows timing, so it catches weeks where large payments and late receipts coincide even when average runway looks comfortable.
How often should I update it?
Weekly. Replace the past week with actual figures, record variances and add a new week at the end.
Should I include expected investment?
Only once it is received. A term sheet or signed agreement may still have conditions, and anticipated money is not cash.
What minimum cash buffer should a startup keep?
It depends on the business. Many founders start with at least one payroll plus statutory payments and adjust for customer concentration.
Do I need accounting software to build one?
No. A spreadsheet is enough to start, as long as it uses actual bank balances and is reviewed weekly.