# Verify receipts and invoices with OpenAI and Slack: n8n workflow

> Started by another system calling it, and works across Google Sheets and Slack. It hands the judgement calls to OpenAI.

Source: https://millionrounds.com/workflow/verify-receipts-and-invoices-with-openai-and-slack (Millionrounds; every figure on the page links to its filing or article)

[Automation library](https://millionrounds.com/workflows) · [Money admin](https://millionrounds.com/workflows?category=Money+admin#library)

# Verify receipts and invoices with OpenAI and Slack

Started by another system calling it, and works across Google Sheets and Slack. It hands the judgement calls to OpenAI. 13 steps, 1 branch: a working afternoon to understand properly.

Medium Calls a model: OpenAI

[Download free](https://millionrounds.com/login?next=%2Fapp%2Fworkflow%2Fverify-receipts-and-invoices-with-openai-and-slack)

**13 steps** Medium: a working afternoon

**1** Branch: places the flow splits

**0** Loops or waits

**2** Services it connects to

## The flow

Starts it 3 Model 2 Logic 5 Service 3

The steps in the order they run, from what starts it.

- 1 **Document Upload Webhook** Webhook *Starts it*
- 2 **Error Trigger** Error trigger *Starts it*
- 3 **OpenAI Chat Model** Lm Chat Open Ai *Model*
- 4 **Normalize Input** Code *Logic*
- 5 **Alert Engineering** Slack *Service*
- 6 **AI Agent** Agent *Model*
- 7 **Parse Extraction** Code *Logic*
- 8 **Build Error Verdict** Code *Logic*
- 9 **Validate Against Booking** Code *Logic*
- 10 **Record Result** Google Sheets *Service*
- 11 **Auto Approve?** If *Logic*
- 12 **Respond** Respond To Webhook *Starts it*
- 13 **Flag For Review** Slack *Service*

## How it's built

- **Starts on:** Another system calling it
- **Steps:** 13, with 1 branch
- **Size:** Medium: a working afternoon
- **Connects to:** Google Sheets, Slack
- **Model:** OpenAI

## Questions

What does it need to run?

An n8n account, plus your own Google Sheets and Slack accounts, and a key for OpenAI. You connect your own accounts after importing it; none are included.

What starts it?

It starts on another system calling it.

Does it use AI?

Yes. It calls OpenAI. Model calls are billed by the provider, not by n8n.

How long does it take to set up?

Plan an afternoon. 13 steps is enough that you should read each one before running it.

How do I import it?

Copy the workflow, open a new workflow in n8n and paste. The steps appear on the canvas, ready for your own accounts.

**Before you run it**

Nothing here has been tested by us. It is somebody's working automation, read and described from its own steps. Treat the connections it wants as a list of accounts it will touch, and read the 13 steps before you point it at anything that matters.

## Run it in n8n

- **Create your n8n account** Free to start. n8n is where the workflow runs. [Create an n8n account ↗](https://millionrounds.com/n8n)
- **Download the workflow** Free with a Millionrounds account. [Download free](https://millionrounds.com/login?next=%2Fapp%2Fworkflow%2Fverify-receipts-and-invoices-with-openai-and-slack)
- **Paste it into n8n** Open a new workflow in n8n and paste. Then connect your own accounts.

Stored with the author's traces removed: canvas notes, instance identifiers, saved credential names and any live document they had left behind.

## Connects to

Each opens the other workflows that use it.

[Google Sheets](https://millionrounds.com/workflows?service=Google+Sheets#library)[Slack](https://millionrounds.com/workflows?service=Slack#library)

## Workflows like it

Also money admin, with the same services where possible, closest in size first.

- [**Compare proposals and analyze gaps for Salesforce CRM** 13 steps · calls a model · Google Drive, Google Sheets](https://millionrounds.com/workflow/compare-proposals-and-analyze-gaps-for-salesforce-crm)
- [**Extract invoice fields from Google Drive to Sheets with Ollama** 13 steps · calls a model · Google Drive, Google Sheets](https://millionrounds.com/workflow/extract-invoice-fields-from-google-drive-to-sheets-with-olla)
- [**Extract structured invoice data from JotForm PDFs with OpenAI** 13 steps · calls a model · Google Sheets](https://millionrounds.com/workflow/extract-structured-invoice-data-from-jotform-pdfs-with-opena)
- [**Generate tax compliance checklists from RSS with Gemini** 13 steps · calls a model · Google Sheets, RSS](https://millionrounds.com/workflow/generate-tax-compliance-checklists-from-rss-with-gemini)
- [**Recommend Salesforce quote pricing with Google Sheets and Groq** 13 steps · calls a model · Google Sheets, Salesforce](https://millionrounds.com/workflow/recommend-salesforce-quote-pricing-with-google-sheets-and-gr)
- [**Recover overdue invoices with OpenAI and Gmail** 13 steps · calls a model · Gmail, Google Sheets](https://millionrounds.com/workflow/recover-overdue-invoices-with-openai-and-gmail)