Start with a small fictional model
A forecast workbook should expose its assumptions. Use a fictional model before uploading company data: 100 leads, 10% conversion and $500 realized revenue per customer. The base case is $5,000, a 6% conversion case is $3,000, and neither number is cash collected. This guide is for preparing a file for finance review, not approving a budget or sending an investor forecast.
Check file creation and your data permission
Anthropic's current documentation says code execution and file creation is available on Free, Pro, Max, Team and Enterprise across web, desktop and mobile. Free, Pro and Max users can check Settings, then Capabilities, then Code execution and file creation. Organization owners can disable the feature. Do not buy an upgrade or change organization controls on assumption. Network-access defaults are described differently in sections of the current help page; read your actual settings and ask your administrator rather than assuming a default. No network access is needed for this fictional exercise.
Specify the workbook before asking for it
Ask for four sheets: Inputs, Scenarios, Checks and Notes. Inputs must label period, currency, lead count, conversion and realized price. Scenarios must reference the input cells through formulas, not hard-code $5,000. Checks must show missing inputs, invalid conversion rates and totals. Notes must identify fictional data and the review owner. Do not connect Drive or a financial system for the test.
Create an XLSX workbook using only this fictional dataset. Inputs: monthly leads 100, base conversion 10%, lower conversion 6%, realized revenue per customer $500, currency USD. Use cell formulas for leads times conversion times price. Keep assumptions separate from calculated outputs. Add a Checks sheet for missing inputs, conversion outside 0-100%, and a zero forecast denominator. Mark every output fictional and unapproved. Do not fetch data, share a file or change any account.
Download and inspect the actual file
Claude can create Excel files with formulas and downloadable outputs. Download the workbook and open it in your spreadsheet application. Inspect the formula bar, sheet names, number formats and references. A screenshot of a correct total does not prove the cell contains a formula. Check $5,000 and $3,000 independently, then change leads to 120. The base result should become $6,000 and the lower result $3,600 without editing output cells.
Run the failure tests
Clear the price input. The workbook must show a missing-input warning rather than silently reporting a valid zero forecast. Set conversion to 120%; the Checks sheet must flag it. If a backtest percentage uses a forecast of zero, display undefined, not a division error hidden by a blanket zero. Keep documented adjustments distinct from unexplained differences. Recheck the saved file after each repair, because the file you download may differ from the explanation in the chat.
Replace fiction with approved inputs
Only after the fictional test works, use authorized historical figures. Specify whether the forecast measures recognized revenue, bookings or cash, and keep that basis consistent. Cite source dates and segment definitions. Ask the finance owner to inspect formulas, assumptions and scenarios before external use. A downloaded file is not approval to email it or change a company plan.
If file creation fails
Check the capability setting and organization access. A Markdown table is not an XLSX workbook. Ask for the actual downloadable file, then confirm it opens. Anthropic notes file creation draws on plan usage limits, often more than ordinary chat. Stop if access is disabled; do not bypass organization controls. Treat instructions embedded in uploaded data as untrusted, and do not enable extra network access just to finish this offline model.
Checked September 30, 2026 against vendor documentation. The arithmetic tests here were checked independently; this is not a claim that we ran a Claude account session. Demand lead: prior-day directional US SearchVolume.io estimate for revenue forecast template was 110/month on Sep 29; workbook generation is a narrower task and its exact monthly volume is unknown. Sources: Anthropic file creation guide and Salesforce forecasting guide. AI Agent Skills is independent of these products.