Lenders, turnaround consultants and private equity portfolio CFOs all reach for the same tool when liquidity is tight: the 13-week cash flow forecast. It is unglamorous, built in a spreadsheet, and tells you with brutal precision which week — if any — you run out of cash. Here's how to build one.
A monthly forecast built off the P&L (the "indirect method" — start with profit, add back non-cash items, adjust for working capital) is good for planning but too coarse for managing liquidity. Within a single month, a business can be cash-positive on day 1, deeply negative by day 20 (after payroll, GST payment and a large supplier payment all land in the same week), and recover by month-end. A monthly view smooths all of this away — and the cash crunch in week 3 is exactly the kind of event that causes a bounced payment or a missed statutory deadline.
The 13-week forecast uses the direct method: instead of starting from profit, you list actual expected cash receipts and payments, week by week, for the next 13 weeks (one quarter).
Rows = cash flow categories. Columns = Week 1 through Week 13, plus an "Opening Balance" column. Categories typically include:
| Section | Line Items |
|---|---|
| Opening Cash Balance | Actual bank balance at start of Week 1 |
| Cash Inflows | Customer collections (by major customer/segment), other income, loan drawdowns |
| Cash Outflows — Operating | Payroll, supplier payments (by major supplier), rent, utilities |
| Cash Outflows — Statutory | GST payment, TDS deposit, advance tax instalments, PF/ESI |
| Cash Outflows — Financing | Loan principal + interest instalments, lease payments |
| Net Cash Flow | Total inflows minus total outflows for the week |
| Closing Cash Balance | Opening + Net Cash Flow — becomes next week's opening balance |
Don't forecast "revenue ÷ 4.3 weeks" — that's a P&L approach. Instead, take your actual outstanding receivables list and, for each significant invoice, estimate the week it will be collected based on the customer's payment history. For new sales expected during the 13 weeks, apply the customer's typical days-to-pay to the expected invoice date. This is the single most important — and most often done badly — step.
List every supplier invoice by its actual due date (not "monthly average"), every statutory due date (GST returns are due on fixed dates; TDS deposits by the 7th of the following month; advance tax on the quarterly due dates), and every loan/lease instalment by its contractual date. These are largely fixed and should be placed in the exact week they fall.
Once populated, scan the closing balance row for the lowest point across the 13 weeks — the "trough." If the trough is negative or below your minimum operating cash requirement (a buffer you set, e.g., one week of payroll + statutory dues), you have 1-12 weeks of lead time to act: delay a discretionary payment, accelerate a collection, draw on a credit line, or negotiate a supplier payment date.
Every week, replace the closing Week 1 with actuals, drop it from the grid, and add a new Week 13 at the end — keeping the rolling 13-week window. Compare actual vs forecast for the week that just closed: large variances (a customer that didn't pay as expected, an unplanned expense) should feed back into how you forecast similar items going forward. Over 2-3 cycles, forecast accuracy typically improves significantly as the model learns the business's real payment patterns.
| Situation | Recommended Cadence |
|---|---|
| Healthy liquidity, stable business | Monthly review is often sufficient — but build the template so it's ready if needed |
| Seasonal business (festive-season-driven, agri-linked) | Weekly during peak working-capital build-up periods |
| Tight covenant headroom (see our DSCR & ICR guide) | Weekly — lenders often request this directly during covenant discussions |
| Turnaround / distress situation | Weekly, non-negotiable — this is the primary management tool |