The short answer: A 13-week cash flow forecast projects every receipt and disbursement week by week for one quarter, ending in a projected bank balance for each week. In the worked example below, the model flags a $12,500 minimum-cash covenant breach 12 weeks before it would happen.
- Thirteen weeks is exactly one quarter (52 ÷ 4), long enough to catch every payroll, renewal, and rent cycle.
- Weekly granularity exposes troughs that month-end balances hide; in the example, one trough sits $160,000 below the October close.
- Build from the reconciled bank balance, the receivables aging, open bills, and the payroll calendar, never from the P&L.
- Roll it every week: drop the finished week, add week 14, and log the variance line by line.
Last updated September 2026.
Month-end cash balances are the numbers most founders watch, and they are the numbers most likely to mislead. Payroll clears on a Friday, a large customer pays on the 28th, and the month closes looking healthy. The low point came nine days earlier.
The weekly format exists to find that low point in advance. The sections below explain why the quarter-long horizon became the standard, what belongs on each line, and how a Series A software company’s model looks when the arithmetic is run in full.
What is a 13-week cash flow forecast?
A 13-week cash flow forecast is a direct-method model of cash in and cash out, laid out in weekly columns for the next quarter. Each week starts with the prior week’s closing balance, adds expected collections, and subtracts expected payments.
The inputs are specific and nameable: this customer’s invoice, this payroll run, this vendor bill. That specificity separates it from a budget or a 12-month plan, which work from drivers and averages. For the broader definition and how a forecast differs from a P&L, see our explainer on what a cash flow forecast is.
Why 13 weeks instead of a monthly or annual view?
Thirteen weeks equals one fiscal quarter, and a quarter is about as far ahead as a finance team can name individual cash events with confidence. Beyond that, the lines turn into estimates.
| Dimension | 13-week forecast | 12-month forecast | Annual budget |
|---|---|---|---|
| Question it answers | Can we cover every obligation, every week? | How long is runway under each plan? | What should each team spend? |
| Method | Direct: named receipts and payments | Indirect or driver-based | Accrual P&L targets |
| Period | Weekly | Monthly | Monthly or quarterly |
| Update cadence | Every week | After each close | Once a year, re-forecast quarterly |
| Input granularity | Individual invoices, bills, and paydays | Drivers and averages | Department targets |
| Owner | Controller or fractional CFO | CFO | CEO and CFO |
The weekly period matters as much as the horizon. In the model below, October closes at $3,202,100, yet week 3 bottoms out at $3,042,100. A monthly forecast would never show the $160,000 gap between those two figures.
What goes into a 13-week cash flow forecast?
Five line groups cover almost every startup: opening cash, customer receipts, payroll, operating payments, and one-time items. Each should trace to a source document.
- Opening cash: the reconciled bank balance, adjusted for outstanding checks and deposits in transit.
- Receipts: open invoices by expected payment week, plus card and ACH subscription collections.
- Payroll: net pay on each payday and employment tax deposits on the IRS schedule.
- Operating payments: bill runs from QuickBooks Online or Bill.com, rent, and debt service.
- One-time items: annual software renewals, insurance premiums, and equipment.
Payroll tax timing trips up many first models. Under IRS Publication 15, an employer that reported more than $50,000 of employment taxes in its lookback period is a semiweekly depositor. The rule reads: “deposit employment taxes for payments made on Wednesday, Thursday, and/or Friday by the following Wednesday.” A Friday payday therefore splits across two forecast weeks.
How do you build a 13-week cash flow forecast from QuickBooks Online?
Start from reconciled cash and work outward through the subledgers. The accounting system supplies most inputs; the forecaster assigns each one to a week.
- Reconcile the bank accounts through the most recent business day and record that balance as week 1 opening cash.
- Export the A/R aging by invoice. Place each invoice in the week the customer historically pays, not the week it falls due.
- Export open bills from QuickBooks Online or Bill.com and slot them into the weekly payment run.
- Lay the payroll calendar over the grid, with net pay on paydays and tax deposits on the IRS schedule.
- Scan contracts for annual and quarterly items: renewals, insurance, and rent escalations.
- Link each week’s opening balance to the prior week’s close, so one formula chain governs all 13 columns.
For a small team without a finance function, the line-by-line 13-week cash flow build walks each row in more detail. Our guide to building a cash flow forecast covers the monthly version.
What does a worked 13-week forecast look like?
Consider an illustrative Series A SaaS company opening the quarter with $3,310,000 of reconciled cash. Its venture-debt agreement requires a $2,500,000 minimum cash balance.
Subscriptions collect $38,700 a week. Two annual invoices land in weeks 4 ($184,000) and 8 ($96,500). Biweekly payroll pays $118,600 of net pay, and each run’s $41,300 tax deposit clears the following week. Bill runs average $21,400 a week, rent is $38,500, and one-time items are a $28,900 insurance premium and a $64,200 software renewal.
| Week | Receipts | Payroll and taxes | Vendors and other | Net cash flow | Closing cash |
|---|---|---|---|---|---|
| 1 | $38,700 | $159,900 | $21,400 | −$142,600 | $3,167,400 |
| 2 | $38,700 | $41,300 | $21,400 | −$24,000 | $3,143,400 |
| 3 | $38,700 | $118,600 | $21,400 | −$101,300 | $3,042,100 |
| 4 | $222,700 | $41,300 | $21,400 | $160,000 | $3,202,100 |
| 5 | $38,700 | $118,600 | $59,900 | −$139,800 | $3,062,300 |
| 6 | $38,700 | $41,300 | $21,400 | −$24,000 | $3,038,300 |
| 7 | $38,700 | $118,600 | $50,300 | −$130,200 | $2,908,100 |
| 8 | $135,200 | $41,300 | $21,400 | $72,500 | $2,980,600 |
| 9 | $38,700 | $118,600 | $59,900 | −$139,800 | $2,840,800 |
| 10 | $38,700 | $41,300 | $21,400 | −$24,000 | $2,816,800 |
| 11 | $38,700 | $118,600 | $85,600 | −$165,500 | $2,651,300 |
| 12 | $38,700 | $41,300 | $21,400 | −$24,000 | $2,627,300 |
| 13 | $38,700 | $118,600 | $59,900 | −$139,800 | $2,487,500 |
Week 1 carries both a payday and the deposit from the prior payroll, so it shows $159,900 of payroll cash.
How does the forecast catch a covenant breach early?
Week 13 closes at $2,487,500, which is $12,500 below the $2,500,000 floor. The model shows the breach in week 1, leaving 12 weeks to act.
Quarterly net burn is $3,310,000 − $2,487,500 = $822,500, or about $274,200 a month. The fix can be small. Converting the $64,200 renewal to quarterly installments of $16,050 defers $48,150 and lifts week 13 to $2,535,650, a $35,650 cushion.
Sensitivity matters as much as the base case. If the $96,500 week-8 invoice slips past week 13, the closing balance falls to $2,391,000 and the shortfall grows to $109,000. The burn rate and runway guide shows how the same net burn feeds the longer runway view.
How often should you update a 13-week forecast?
Every week, on the same day. Replace the finished week’s projections with actual bank activity, add a new week 13 at the end, and record the variance for each line.
The variance log is the quality control. If receipts miss by more than 10% for three consecutive weeks, the collection assumptions need rebuilding. The same discipline applies to the monthly variance analysis at close, which checks whether the actuals feeding the forecast are right.
Who should own the 13-week forecast at a startup?
A controller or fractional CFO should own it, with the founder reviewing it weekly. The owner needs access to the bank, the subledgers, and the payroll calendar, plus the authority to ask sales when a large invoice will actually pay.
The forecast is only as reliable as the books behind it. Under the Continuous Close Method™, reconciliations run as transactions land, so opening cash for each weekly roll is already reconciled. Kevin Cahill typically sets the minimum-cash threshold and the weekly review time with founders before the first model is built. Our outsourced CFO services include the weekly roll and the variance commentary.
Frequently asked questions
What is a 13-week cash flow forecast?
It is a weekly, direct-method projection of cash receipts and disbursements for the next quarter. Each week opens with the prior week’s closing balance, adds named collections, subtracts named payments, and ends in a projected bank balance. The format shows the lowest cash point in the quarter, which month-end balances often hide.
Why 13 weeks and not a monthly or annual view?
Thirteen weeks is one fiscal quarter, the furthest horizon over which most finance teams can name individual receipts and payments with confidence. Weekly periods capture payroll, tax deposit, and collection timing inside a month. In the worked example, the week-3 balance sits $160,000 below the October close.
How do you build a 13-week cash flow forecast from QuickBooks Online?
Reconcile the bank accounts and use that balance as opening cash. Export the A/R aging by invoice and place each receipt in the week the customer usually pays. Export open bills, overlay the payroll calendar and IRS deposit schedule, add annual contract items, and link each week’s opening balance to the prior week’s close.
How often should you update a 13-week forecast?
Update it weekly on a fixed day. Replace the completed week with actual bank activity, add a new week at the end so the horizon stays at 13 weeks, and log the variance for each line. Receipts that miss by more than 10% for three straight weeks signal that collection assumptions need rebuilding.
How is a 13-week forecast different from your annual budget?
The budget sets accrual-basis spending targets for the year and is revised quarterly at most. The 13-week forecast tracks actual cash timing week by week and is rebuilt every week. A company can be on budget and still breach a minimum-cash covenant in a single week.
Who should own the 13-week forecast at a startup?
A controller or fractional CFO should own the model, and the founder should review it weekly. The owner needs bank access, the subledgers, the payroll calendar, and a direct line to sales for expected payment dates on large invoices. Accurate forecasts depend on reconciled books at every weekly roll.
