# How to build a 13-week cash flow forecast with AI: QuickBooks + Stripe

> Refresh a 13-week cash flow forecast with Claude, Copilot or ChatGPT in Excel: the files, three prompts, the tie-out checks and how to repeat it every Monday.

- **URL**: https://www.nocodetalks.co/blog/13-week-cash-flow-forecast-with-ai
- **Author**: Ankur Khandelwal, Nocodetalks
- **Updated**: Oct 7, 2026
- **Topic**: Cash & CFO
- **Sources checked**: 24

---

_For CFOs, controllers and CAS teams who already run a 13-week._ Which AI surface to use, the files it needs, three prompts for the Monday refresh, and the checks that catch what the AI gets wrong.

## The short answer

Keep the 13-week model in Excel with live formulas, and let an AI inside the workbook do the Monday refresh: Claude in Excel, Copilot in Excel or ChatGPT for Excel. Give it the QuickBooks A/R and A/P aging, bank balances and Stripe payouts, and have it spread receipts on each customer's real days-to-pay, roll the week forward and explain the variance against last week's file. Then tie opening cash to the bank and receipts to the aging yourself before anyone sees it.

## What you need: one AI surface and these files

You know the method. The choices are where the AI sits and what it reads. Here are the options as of October 2026; start with the first one your firm allows.

| Surface | Best for | Watch out for |
|---|---|---|
| **Claude in Excel** (add-in; Pro, Max, Team, Enterprise) | Refreshing a model you trust. It keeps formula links intact and cites the cells it used. | No macros, VBA or data tables. Chat history stays in your browser, so the method has to live in the workbook or a skill. |
| **Copilot in Excel** (edit mode) | Firms that only allow Microsoft. With a commercial Copilot or Microsoft 365 Premium license you can pick a Claude or GPT model. | An admin has to enable Anthropic models before you can choose Claude. |
| **ChatGPT for Excel** | Teams already on ChatGPT. It's on every plan (Free and Go with limited use) and supports skills and apps. | OpenAI says VBA and macros may not be fully supported. Duplicate the file before big edits. |
| **Claude Cowork** or **Claude Code** on a folder | Many clients, one folder each, with exports dropped in every Monday. | Since October 6, 2026, new Cowork sessions on Pro and Max run in Anthropic's cloud. For local-only work Anthropic points to Claude Code in the desktop app. |
| **Connectors** (QuickBooks, Xero, Stripe) | Reading aging reports, balances and payouts without exporting. | Intuit's QuickBooks connector lists A/R aging but not A/P aging. Xero's connector reads both and is read-only. |

**Have these ready each Monday:**

- Last week's saved forecast. It's your variance baseline, so never overwrite it.
- Bank balances as of the forecast date, plus the credit line's commitment and current availability.
- A/R aging detail and A/P aging detail or Unpaid Bills. On QuickBooks Simple Start, use Open Invoices for receipts.
- Twelve months of paid invoices with invoice and payment dates. This is what lets the AI use real days-to-pay instead of terms.
- The payroll calendar, the Stripe payouts list and the owner's list of one-off items.

> Note: Forecast Stripe payouts, not gross charges. Stripe takes fees, refunds and disputes out of the balance before it pays out. Invoices paid through Stripe also sit in the A/R aging, so keep that cash on one row.

## The weekly 13-week cash flow workflow with AI

The first run takes the longest. After that, Monday is a refresh of the same file.

1. **First run only: audit the data.** You attach the A/R export and payment history. The AI flags duplicates, terms written five ways, credit memos and blank dates, then works out each customer's days-to-pay. CJ Gustafson's Claude demo does this before building anything ([Run the Numbers, 5:07](https://youtu.be/-8W_F3RwlRM?t=307)).
2. **Save a copy.** Duplicate last week's file and date it. The AI edits the copy only.
3. **Load fresh data.** Paste this week's exports into the input tabs, or let a read-only connector pull them.
4. **Roll forward.** The AI moves week 1 to history with actuals, adds a new week 13 and re-spreads open invoices on days-to-pay. You approve each edit.
5. **Explain the variance** against last week's forecast, line by line, and flag any week below your minimum cash.
6. **Stress one assumption.** Your largest customer pays two weeks late: is every payroll still covered? Peta-Gaye Hardy runs this build, low-point and late-payer sequence in ChatGPT from three files ([4:13](https://youtu.be/Wda3Y2zRR3g?t=253)).

> Net 30 is just a story you've been telling your own forecast.
> — CJ Gustafson, Run the Numbers (YouTube, June 2026) (https://youtu.be/-8W_F3RwlRM?t=47)

Prompt for Claude · First run: audit the data and learn how customers pay:

```
I'm building a 13-week cash forecast starting Monday [DATE].
Attached: [A/R aging detail], [12 months of paid invoices with invoice and payment dates], [A/P aging], [payroll calendar].
Before building anything:
1. Audit the data. List duplicates, inconsistent terms, credit memos, blank dates and anything you can't interpret.
2. For each customer, calculate average days from invoice to payment and the range. Flag anyone paying more than [15] days past terms.
3. Ask me each decision as a short multiple-choice question.
Show your workings on a separate tab. Mark every figure you inferred rather than read from the files. Don't change the source data.
```

The next two prompts work the same way in Copilot in Excel or ChatGPT for Excel. Run them on the dated copy.

Prompt for Claude · Monday roll-forward inside the workbook:

```
This is a copy of last week's 13-week forecast. The [Inputs] tab now has this week's bank balances, A/R aging, A/P aging and Stripe payouts.
1. Move week 1 to [History] with actuals from [Actuals].
2. Add a new week 13. Extend every formula. Don't type values into calculated cells.
3. Re-spread open invoices using the days-to-pay table on [Customers]. Put anything over [90] days past due on the at-risk line.
4. List every cell you changed and every assumption you made.
Ask before editing outside these tabs. If an input looks wrong, stop and tell me.
```

Prompt for Claude · Variance against last week's forecast:

```
Compare last week's forecast for week [N] on [Saved forecast] with actual cash for that week on [Actuals].
For each line, show forecast, actual, variance and a one-sentence reason.
Use only reasons supported by the data or by my notes: [NOTES]. If neither explains a variance, write 'needs input' instead of guessing.
Then flag any of the next 13 weeks where closing cash falls below $[MINIMUM] and name the line driving it.
Keep facts and interpretation in separate columns.
```

## Check the forecast before you send it

Several demos have the AI check its own work. That helps, but it isn't a tie-out. Do these yourself every week.

- **Opening liquidity reconciles.** Week 1 opening cash equals the bank, and credit availability is the lower of the borrowing base and the facility commitment. In a Luke Finance demo on fictional data, Claude found treasury had reported availability on a borrowing base above the $60M revolver cap, a $6.58M overstatement, and reran the model on the corrected figure ([21:37](https://youtu.be/araz7e2DzX8?t=1297); sponsored by Higgsfield).
- **Receipts tie to the aging.** Receipts in weeks 1 to 13, plus the at-risk line, plus anything expected after week 13, equal the A/R aging total. Run the same test for A/P.
- **Formulas are live.** Press F5, then Special, then Constants to show hard-coded numbers ([CFI, 14:38](https://youtu.be/BX2PxxM15Zc?t=878)). Then change one input and watch closing cash move. Josh Aharonoff found hard-coded tabs in a Claude-built model ([18:05](https://youtu.be/m5YF89Kym1Y?t=1085); he sells a competing Excel add-in).
- **The corkscrew holds.** Each week's closing cash equals opening plus receipts minus disbursements, and becomes next week's opening.
- **Payroll is on every pay date,** including three-payroll months. Luke's demo calls the commitments schedule the file people leave out, and payroll was the largest outflow in it ([20:55](https://youtu.be/araz7e2DzX8?t=1255)).
- **Five numbers match the source.** Pick five cells at random and trace them to QuickBooks, Stripe or the bank.

> Note: An AI's self-review isn't proof. In Luke's demo, Claude's verification pass found five errors in its own draft ([23:19](https://youtu.be/araz7e2DzX8?t=1399)). Shin Financials reports the opposite: asked to review every formula, the AI said all was fine while some calculations were off ([14:20](https://youtu.be/shNYNFFCz2g?t=860)).

## Make it repeat every Monday

Recurring AI reports drift in format. The fix people report is moving the method out of the prompt and into a file.

1. **Have the AI write the spec.** After a good run, ask it to reverse-engineer what it just did into reusable instructions. Mike Dion does this in Cowork, then attaches the result to a Monday 8 a.m. task ([17:01](https://youtu.be/3wN5c0yDltg?t=1021)).
2. **Save it as a skill.** A skill is a folder with a SKILL.md file. Claude, ChatGPT and Copilot in Excel all use this format; Copilot reads custom skills from a OneDrive folder. Put your layout, the days-to-pay method, the minimum cash and the checks above in it.
3. **Keep the weekly prompt short.** Name the skill and the date, nothing more, so there's only one copy of the logic.
4. **Borrow a starting point.** Anthropic's official small-business plugin (anthropics/knowledge-work-plugins, about 27,000 stars) has a cash-flow-snapshot skill. It measures each customer's payment lag but forecasts 30, 60 and 90 days, so adapt it to weekly columns.

**About scheduling.** Anthropic says scheduled Cowork tasks now run in its cloud, so your computer doesn't need to be awake. But a cloud session can only read a connected local folder while the desktop app is open, which is why Dion's May demo says to leave Claude Desktop running ([18:21](https://youtu.be/3wN5c0yDltg?t=1101)). Anthropic's own safety guide also says not to schedule tasks that access sensitive files. A simple rule for client books: schedule a reminder or a read-only pull, and run the refresh yourself.

What people report
- A VP of product at an accounting firm said board packs and month-end reports stopped drifting once the spec lived in a markdown file the agent reads on every run. (a commenter on r/CFO (April 2026), https://www.reddit.com/r/CFO/comments/1sqxcw7/what_we_use_ai_for_in_finance/)
- An FP&A user said Cowork connected to NetSuite now updates their 13-week model with forecast and actuals. It took a lot of troubleshooting at first. (a commenter on r/FPandA (2026), https://www.reddit.com/r/FPandA/comments/1u84k4y/are_people_using_claude_if_so_what_are_you_using/)

## Where AI fails on a 13-week forecast

- **It doesn't know what was promised.** Which customer said Friday, which vendor will wait. Those notes come from you.
- **Missing inputs shrink the forecast quietly.** Luke's source files had no term-loan interest. Claude flagged it and said the forecast wasn't decision grade beyond week six ([26:38](https://youtu.be/araz7e2DzX8?t=1598)).
- **Risk ratings can be framed wrong.** Dion's demo rated one location critical for today's overdraft and another only moderate despite a 30.6% forward drop ([11:40](https://youtu.be/3wN5c0yDltg?t=700)).
- **Demos use clean, made-up companies.** Every 13-week demo cited here runs on fictional data. Real multi-entity books are messier.

What finance people say
- One commenter said they trust AI to build systems, but not to hand them a number unless it's simple to verify. Another saw Claude turn 3.87% into 3.4% in a basic report. (commenters on r/CFO (April 2026), https://www.reddit.com/r/CFO/comments/1sqxcw7/what_we_use_ai_for_in_finance/)
- Several commenters said finance AI tools look good in demos and get messy with real multi-entity books. (commenters on r/CFO (May 2026), https://www.reddit.com/r/CFO/comments/1tlozld/has_anyone_actually_found_an_ai_finance_tool_that/)

## Data safety

Use a business plan that doesn't train on your data, and give the AI copies, not originals. Connect QuickBooks, Xero and Stripe read-only where you can, and turn on tool approval, as Stripe's docs advise; its server can also write. Since October 6, Pro and Max Cowork sessions run in the cloud and fetch copies of the files a task needs. Claude in Excel deletes inputs on the backend within 30 days but isn't in Enterprise audit logs. Before client books go in, read [is Claude safe for client data](https://www.nocodetalks.co/blog/is-claude-safe-for-client-data).

## Common questions

**Which AI is best for a 13-week cash flow forecast?**

The one that works inside your existing workbook and that your firm allows. Claude in Excel, Copilot in Excel and ChatGPT for Excel all edit live workbooks. Reddit threads lean toward Claude, but many firms allow only Copilot, and Copilot can run Claude models if your license and admin allow it.

**Can AI pull QuickBooks and Stripe data into the forecast automatically?**

Partly, as of October 2026. Intuit's QuickBooks connector reads the A/R aging but doesn't list A/P aging, so export that. Xero's connector reads both, read-only. Stripe's MCP server can read balances and list payouts. Bank balances still come from the bank or a bank connector.

**Can I schedule the forecast to run every Monday?**

Yes, with care. Scheduled Cowork tasks run in Anthropic's cloud, but they can only read a local folder while the desktop app is open, and Anthropic advises against scheduling tasks that access sensitive files. For client data, schedule the reminder and run the refresh yourself.

**Should the AI build the model from scratch each week?**

No. Build or vet the model once, save it, and have the AI refresh it. A model you've reviewed is far easier to check than a new one every Monday.

**Should the forecast include new sales?**

Creators disagree. Gustafson argues the next 13 weeks are mostly already on the balance sheet for B2B companies. Hardy's ChatGPT model includes expected new sales. Pick one approach, write it into your skill and label the line.

## Sources

- [How to Build a 13-Week Cash Flow Forecast in Claude](https://youtu.be/-8W_F3RwlRM?t=307)
- [Claude For CFOs: 3 INSANE Use Cases](https://youtu.be/araz7e2DzX8?t=1297)
- [I Used Claude to Build a Cash Flow Forecast That Runs Itself Every Monday](https://youtu.be/3wN5c0yDltg?t=1021)
- [I Built a 13-Week Cash Flow Forecast in ChatGPT (From Just 3 Files)](https://youtu.be/Wda3Y2zRR3g?t=253)
- [Testing Claude in Excel: Building a Three-Statement Financial Model](https://youtu.be/BX2PxxM15Zc?t=878)
- [Testing Claude for Excel: Can It Build a Real Financial Model?](https://youtu.be/m5YF89Kym1Y?t=1085)
- [1 Month of Claude in Finance](https://youtu.be/shNYNFFCz2g?t=860)
- [Use Claude for Excel](https://claude.com/docs/office-agents/excel)
- [Use Claude Cowork on web, desktop and mobile](https://support.claude.com/en/articles/15520349-use-claude-cowork-on-web-desktop-and-mobile)
- [Use Claude Cowork safely](https://support.claude.com/en/articles/13364135-using-cowork-safely)
- [Frequently asked questions about Copilot in Excel (edit, plan and chat modes)](https://support.microsoft.com/en-us/office/frequently-asked-questions-about-agent-mode-in-excel-1cfd906d-40b4-46be-8e2d-65b893e28a02)
- [Use skills with Copilot in Excel to complete repeatable tasks](https://support.microsoft.com/en-us/excel/copilot/copilot-in-excel-skills)
- [ChatGPT for Excel and Google Sheets](https://help.openai.com/en/articles/20001063-chatgpt-for-excel-and-google-sheets)
- [What are Skills?](https://support.claude.com/en/articles/12512180-what-are-skills)
- [Skills in ChatGPT and Codex](https://learn.chatgpt.com/docs/build-skills)
- [QuickBooks connector (Intuit)](https://claude.com/connectors/quickbooks)
- [Xero connector](https://claude.com/connectors/xero)
- [Model Context Protocol (MCP)](https://docs.stripe.com/mcp)
- [Balances and settlement time](https://docs.stripe.com/payments/balances)
- [Reports included in your QuickBooks Online subscription](https://quickbooks.intuit.com/learn-support/en-us/help-article/purchase-orders/reports-included-quickbooks-online-subscription/L0s4KrGgr_US_en_US)
- [anthropics/knowledge-work-plugins: small-business plugin, cash-flow-snapshot skill](https://github.com/anthropics/knowledge-work-plugins/tree/main/small-business)
- [What we use AI for in Finance](https://www.reddit.com/r/CFO/comments/1sqxcw7/what_we_use_ai_for_in_finance/)
- [Are people using Claude? If so, what are you using it for?](https://www.reddit.com/r/FPandA/comments/1u84k4y/are_people_using_claude_if_so_what_are_you_using/)
- [Has anyone actually found an AI finance tool that holds up beyond the demo stage?](https://www.reddit.com/r/CFO/comments/1tlozld/has_anyone_actually_found_an_ai_finance_tool_that/)