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ChatGPT buckets lines into weeks with Python, computes positions and drafts the assumptions register. You read code and sign off.
Build the workbook
Place and compute
Review and sign off
Use: You
Put four lists in one workbook, one header row per tab, plus an assumptions tab with collection timing per band, start date and opening balance.
The collection-timing assumptions must be yours, not guesses; ageing alone does not say when customers pay. Check your organisation's rules for restricted finance data before uploading it to any tool; this record does not establish that upload is permitted.
Use: ChatGPT
Upload the workbook; ChatGPT assigns each line to forecast weeks, computes opening and closing positions per week, flags negative weeks and drafts the assumptions register.
What to paste into the tool
Task: Weekly cash flow table with a source row or assumption reference on every line. Using only the uploaded workbook and its assumptions tab, place every line into one of 13 weeks starting on the stated date. Output week, line type, source tab and row or assumption name, and amount. List lines you could not place. Do not invent amounts or dates. Task: Forecast table with running positions, flagged weeks and a draft assumptions register. From the weekly table and the opening balance on the assumptions tab, compute opening and closing position for each week. Mark every week with a negative closing position without adjusting it. Draft an assumptions register listing each assumption used, where it was applied and which lines it affects. Mark anything you inferred as a question.
Use: You
Read the generated code and outputs, recompute the first and last week by hand, confirm each assumption and sign off the draft.
Every figure must be source-linked or assumption-labelled. Funding decisions are outside this workflow. Treat the forecast as a planning draft, not liquidity assurance; make no payment promises from it.
The forecast lives as Google Sheets formulas. Gemini builds grid, balances, flags and register; you trace each formula and approve.
Build the tabs
Build grid and balances
Confirm and approve
Use: You
Have ready: AR ageing, AP register, payroll and recurring items, loaded as Sheet tabs with an assumptions tab for timing, start date and opening balance.
Convert any Excel source to a native Google Sheet first. Check your organisation's rules for restricted finance data before uploading it to any tool; this record does not establish that upload is permitted.
Use: Gemini
Ask Gemini in Sheets for the 13-week grid with week-sum formulas, running balance formulas with negative-week flags, and draft register rows.
What to paste into the tool
Task: Google Sheet with a 13-week grid, week formulas and a source reference column. Create a 13-week grid from the forecast start date. Suggest formulas that sum AP register amounts due in each week, move AR amounts to the week implied by the assumption for their ageing band, and sum payroll and recurring items. Show the ranges used. Label every line with its source tab or its assumption. Task: Google Sheet with closing positions and flagged weeks. Add opening and closing balance formulas for each week, starting from the opening cash balance on the assumptions tab, and a flag on every week with a negative closing balance. Do not smooth, round away or hide negative weeks. Task: Google Sheet with a draft assumptions register. Draft one register row per assumption on the assumptions tab: what it assumes, which lines it touches, where the formula uses it. Add nothing that is not on the tab.
Use: You
Check the sheet against your own facts: every figure traces to a source tab or stated assumption, then approve as the draft forecast.
Negative weeks stay visible. Open each formula and trace it to its source range. Compare three weeks of inflows, outflows and closing balances with a hand total. Delete any register row naming an assumption not on the tab.
You place each flow into its week. Claude recomputes positions from your table as an independent check, builds a formula workbook.
Place the flows
Recompute and build
Confirm and approve
Use: You
Place each receivable, payable, payroll and recurring line into its week in spreadsheets, noting source or assumption, plus start date, opening balance and collection assumptions.
State the collection assumption beside every receivable. Check your organisation's rules for restricted finance data before uploading it to any tool; this record does not establish that upload is permitted.
Use: Claude
Upload a weekly table; Claude recomputes weekly totals and positions in code, lists unreferenced lines, builds an Excel workbook with formulas, flags and a register.
What to paste into the tool
Task: Independent recomputed totals and a list of unreferenced lines. Recompute weekly inflow, outflow, opening and closing position from this table only, using the stated start date and opening balance. List any line with no source row or assumption reference. Do not correct figures; report differences. Task: Excel file with formulas, flag column and register sheet. Create an Excel workbook from this table with formulas for opening and closing position, a flag column for negative closing weeks, and an assumptions register sheet containing only the assumptions I listed.
Use: You
Check the workbook against your own facts, confirm each assumption, decide management actions and approve the workbook as the draft forecast.
Check flagged weeks match the negative closing positions.
Best when: Placement and arithmetic in one conversation
What it does: ChatGPT computes; you review code and sign off
Strong at: Single trail holds table, maths and register
Limit: You must read the generated code yourself
Free plan: Yes, limited (uploads and analysis capped)
Best when: Visible formulas others can inspect and re-run
What it does: Gemini builds the grid; you trace and approve
Strong at: Tracing a line to source is a cell lookup
Limit: Needs an eligible Workspace or Google AI plan
Free plan: Yes, limited
Best when: You own placement; AI is the second pass
What it does: You place; Claude recomputes independently
Strong at: A separate recompute checks your table
Limit: Week placement is done by hand
Free plan: Yes
Before you paste into any AI tool, remove any confidential information. Put it back at the end.
Deciding between ChatGPT and Claude for this? See the comparison.
Never paste credentials or full payment details.
Finance manager confirms every collection-timing assumption.
Every line carries a source row or an assumption label.
Negative weeks are flagged and left visible.
Check data-handling rules for restricted data before any upload.
Check the result against your original inputs. Approve it before sharing or acting.