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Build a 13-week rolling cash forecast

Generate a weekly cash forecast model from AR aging, AP terms, payroll cadence, and known one-time inflows/outflows.

Workflow · Cash & Liquidity | Role · Finance Director | Advanced | 12 min | Updated 20260421
The prompt

Copy and customize

prompt.txt
You are a senior Finance Director producing the following deliverable: build a 13-week rolling cash forecast.

Context
- Workflow: Cash & Liquidity
- Inputs available: {paste the data here}
- Period: {month / quarter}
- Audience: {who reads this}

What to produce
1. The headline takeaway in one sentence.
2. The three things that materially moved the result, with quantified contribution.
3. The one risk or anomaly worth flagging.
4. A short forward-looking note: what to watch next period.

Guardrails
- Use only the numbers provided; do not invent values.
- Cite a row reference for every claim.
- Flag anything you cannot reconcile rather than smoothing it over.
Open in
We’ll copy the prompt and open the chat.
How to use

Run it in four steps

  1. Assemble AR aging with payment-term overrides, AP terms for at least your top 20 vendors, the payroll calendar, and any known one-time flows for the next 13 weeks.
  2. Reconcile opening cash to the bank, then paste the inputs into {paste the data here} and set the forecast start in {month / quarter}.
  3. Run it and check week 1 against your actual bank balance before trusting weeks 2 through 13.
  4. Re-run whenever a large receipt or payment moves week, since the model assumes the timing you gave it.
When to use

When to reach for this prompt

Run weekly — typically Monday morning — as part of the treasury rollforward. The first run takes longer; subsequent runs should take under ten minutes once your AR/AP pulls are templated. Don't use this prompt for board-level cash projections beyond 13 weeks. Accuracy drops off sharply past the AR aging horizon.
Example output

What you can expect back

Week-ofInflowOutflowNetEnding Cash
W01$2.1M$1.8M+$0.3M$12.3M
W02$1.9M$2.4M-$0.5M$11.8M
W03$2.4M$1.7M+$0.7M$12.5M
W07$1.6M$3.0M-$1.4M$9.1M ← trough

Watch: Week 7 dips to $9.1M (payroll + quarterly tax payment).

Run-rate burn assumption: $4.8M/mo opex.

Limitations · Worth knowing

This prompt has real limitations you should understand.

Only as good as your AR aging. If your largest customers pay outside of stated terms, the inflow timing is fiction — manually override known-late payers or the forecast will be optimistic on weeks 4-8.
01

Promised pay dates lie

AR aging shows what is owed, not when it will pay. Without a customer-level pattern of actual-vs-promised, the prompt assumes invoices pay on terms — and the inflow timing in weeks 4-8 becomes optimistic fiction.

02

AP timing is a choice

Vendors get paid when finance decides to pay them, not on the AP terms in the system. The prompt cannot see your treasury team's stretching strategy, so the outflow timing will be too even.

03

One-offs dominate the trough

The worst week in the forecast is usually driven by a single payroll, tax, or true-up event. Miss one in your override list and the trough either disappears or appears in the wrong week — and your covenant headroom goes with it.

Prerequisites

What your data needs to look like

  • Current AR aging with customer-level payment-term overrides
  • AP terms by vendor (or at least top 20 by spend)
  • Payroll schedule with exact run dates
  • Known one-time inflows/outflows for the next 13 weeks
  • Opening cash balance reconciled to bank
See it run on real data

See how FinanceOS handles this prompt on real financial data.

Book a 20-minute walkthrough. We’ll run this exact prompt against a sample dataset reconciled through FinanceOS, and show you what changes when the data underneath is right.

Book a walkthrough
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