Cash flow forecasting itself — the calculations, the model, the formulas — belongs in your spreadsheet. That is not a job for Claude. But every forecast also needs a story: the assumptions behind it, the scenarios it covers, and the commentary that explains what the numbers mean to the people reading them.
That narrative layer is where Claude adds real value. You build the model and run the numbers in your spreadsheet. Claude turns the output into a clear scenario narrative, a set of documented assumptions, and commentary that explains what is driving the forecast — ready for the people who need to understand it, not just see it.
Key insight: Claude does not calculate your forecast. It explains it. Keep the maths in your spreadsheet — use Claude for the assumptions documentation, scenario narrative and commentary that sits around the numbers.
Best case
Claude documents the assumptions driving the upside scenario in plain language for stakeholders.
Base case
Claude writes the core narrative — what the forecast assumes and why it is the most likely outcome.
Worst case
Claude explains the downside triggers and what would need to happen for this scenario to occur.
Assumptions documentation — written once, reused every forecast cycle
13-week cash narratives — turned from raw weekly figures into a clear story
Board-ready commentary — scenario summaries for non-finance stakeholders
These three prompts cover the narrative side of cash flow forecasting. Run your model first — then use these prompts on the output.
Key insight: Always give Claude the assumptions behind your numbers, not just the numbers themselves. A forecast figure without its assumption is just a number — Claude needs the "why" to write a useful narrative.
Prompt 1 — 13-week cash flow narrative
Act as a Finance Manager. Write a narrative summary of the following 13-week cash flow forecast for senior management.
Opening cash position: [figure]
Weekly cash in/out summary: [Paste your weekly figures — inflows and outflows]
Lowest projected cash week: [Week number and figure]
Key assumptions: [e.g. "Customer X payment assumed in week 6", "No new funding drawn"]
Format: one paragraph overview of the 13-week trend, a flag for the lowest cash point with [WATCH] if it falls below [your minimum threshold], and a short list of the key assumptions underlying the forecast.
Prompt 2 — Scenario narrative (best / base / worst case)
Act as a Finance Business Partner. Write a scenario narrative comparing the following three cash flow scenarios.
Base case — closing cash position and key assumptions: [figures and assumptions]
Best case — closing cash position and what changes from base: [figures and assumptions]
Worst case — closing cash position and what changes from base: [figures and assumptions]
Format: one short paragraph per scenario explaining what drives the difference from the base case, followed by a summary sentence on the range of outcomes. Plain language — suitable for a non-finance board audience.
Prompt 3 — Forecast assumptions documentation
Act as a Financial Controller. Turn the following list of forecast assumptions into a clear, structured assumptions document for the forecast model.
Assumptions (in any order): [List each assumption — e.g. "Revenue grows 3% month on month", "Payment terms remain 30 days", "No new hires before Q3"]
Forecast period: [e.g. 13 weeks / FY2026]
Owner of the forecast: [Role title]
Format: group assumptions under headings (Revenue, Costs, Working Capital, Other). For each assumption, state it clearly in one sentence and note whether it is conservative, neutral or optimistic relative to recent actuals.
Cash flow forecasts directly inform decisions about funding, payment timing and supplier relationships — getting the workflow right matters.
Key insight: The model lives in your spreadsheet. Claude lives around it — assumptions, narrative, scenarios. Keeping this separation clear is what makes the workflow safe and repeatable.
1
Build and run your model first
Your cash flow model — formulas, links, scenario toggles — stays in Excel or Google Sheets. Claude does not build or verify the model itself.
2
Export the output, not the formulas
Paste the resulting figures — opening position, weekly movements, scenario outcomes — into Claude. The formulas and underlying model stay in your spreadsheet.
3
Always include the assumptions
Every figure should come with the assumption behind it. This is what lets Claude write a narrative that explains the "why", not just the "what".
4
Verify the narrative against the model
Read the output back against your model before sharing. Claude should describe what your forecast shows — if it does not match, the input was incomplete or unclear.
Important: Claude does not replace your forecasting model or your judgement on funding decisions. It produces narrative and documentation from figures you provide — every figure and assumption must be verified against your model before the forecast is shared or acted upon.