Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase

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1. Workflow Overview

How it works Monitors your AP inbox for incoming invoices, extracts structured data with AI, runs duplicate and vendor history checks against Supabase, then scores each invoice for fraud risk — ...

Best for

Invoice Processing automation workflows
AI Summarization automation workflows
advanced n8n builders looking for reusable templates

Tools used

n8n-nodes-base.stickynote, n8n-nodes-base.gmailtrigger, @n8n/n8n-nodes-langchain.agent, @n8n/n8n-nodes-langchain.lmchatopenai, @n8n/n8n-nodes-langchain.outputparserstructured, n8n-nodes-base.supabase, n8n-nodes-base.code, n8n-nodes-base.if

Source and attribution

This workflow is cataloged by N8N Workflows and links back to its original n8n.io source page by Kumar SmartFlow Craft.

Original n8n.io source

1.1 Workflow description

Title: Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase
Workflow name: Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase

🚀 How it works

Monitors your AP inbox for incoming invoices, extracts structured data with AI, runs duplicate and vendor history checks against Supabase, then scores each invoice for fraud risk — routing suspicious ones to Slack and your AP team before any payment is processed.

📬 Gmail Trigger monitors your accounts payable inbox in real time
🤖 AI Agent extracts invoice number, vendor, amount, currency, dates and line items into structured JSON — no manual data entry
🔍 Checks Supabase for duplicate invoice numbers already in the system
🏢 Checks vendor payment history — flags unknown vendors and amount deviations above 50% from the vendor's historical average
🧠 Second AI Agent scores fraud risk: low / medium / high / critical with specific fraud indicators and a recommended action
🚨 High/critical risk — posts a detailed Slack alert to #invoice-alerts and emails your AP manager with a hold notice
🗄️ Logs every processed invoice to Supabase with risk score and status

🛠️ Set up steps

Estimated setup time: ~20 minutes

Gmail Trigger — connect Gmail OAuth2; point it at your AP inbox
OpenAI — connect OpenAI API credential (used by both AI Agent nodes)
Supabase — connect Supabase API credential; create two tables: invoices (invoice_number, vendor_name, amount, status, risk_level, created_at) and vendors (vendor_name, avg_amount, total_invoices, flagged)
Slack — connect Slack OAuth2; update the channel name #invoice-alerts
Gmail (Send) — connect Gmail OAuth2; replace [email protected]
Follow the sticky notes inside the workflow for per-node guidance

📋 Prerequisites

Gmail account receiving invoices
OpenAI API key (GPT-4o)
Supabase project with invoices and vendors tables
Slack workspace with an alerts channel

Custom Workflow Request with Personal Dashboard

[email protected]

https://www.smartflowcraft.com/contact

More free templates

https://www.smartflowcraft.com/n8n-templates

1.2 Logical Blocks

This catalog entry is organized from the workflow JSON. The node-level section below shows the executable blocks available for review before importing the template.

2. Block-by-Block Analysis

Block 1 - Overview

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 2 - Prerequisites

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 3 - Setup Required

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 4 - How It Works

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 5 - Gmail — Invoice Inbox

Type / Role: n8n-nodes-base.gmailTrigger - gmailTrigger
Config choices: Version 1.2

Block 6 - Extract note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 7 - Extract Invoice Data

Type / Role: @n8n/n8n-nodes-langchain.agent - agent
Config choices: Version 1.8

Block 8 - OpenAI — Extract

Type / Role: @n8n/n8n-nodes-langchain.lmChatOpenAi - lmChatOpenAi
Config choices: Version 1.2

Block 9 - Invoice Data Schema

Type / Role: @n8n/n8n-nodes-langchain.outputParserStructured - outputParserStructured
Config choices: Version 1.2

Block 10 - Duplicates note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 11 - Check Duplicates

Type / Role: n8n-nodes-base.supabase - supabase
Config choices: Version 1

Block 12 - Count Dup note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 13 - Count Duplicates

Type / Role: n8n-nodes-base.code - code
Config choices: Version 2

Block 14 - Vendor note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 15 - Check Vendor History

Type / Role: n8n-nodes-base.supabase - supabase
Config choices: Version 1

Block 16 - Merge Context note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 17 - Merge All Context

Type / Role: n8n-nodes-base.code - code
Config choices: Version 2

Block 18 - Risk note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 19 - Assess Fraud Risk

Type / Role: @n8n/n8n-nodes-langchain.agent - agent
Config choices: Version 1.8

Block 20 - OpenAI — Risk

Type / Role: @n8n/n8n-nodes-langchain.lmChatOpenAi - lmChatOpenAi
Config choices: Version 1.2

Block 21 - Fraud Risk Schema

Type / Role: @n8n/n8n-nodes-langchain.outputParserStructured - outputParserStructured
Config choices: Version 1.2

Block 22 - High Risk note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Block 23 - High Risk?

Type / Role: n8n-nodes-base.if - if
Config choices: Version 2.2

Block 24 - Slack note

Type / Role: n8n-nodes-base.stickyNote - stickyNote
Config choices: Version 1

Showing the first 24 of 28 workflow blocks. Download the JSON for the full node graph.

3. Summary Table

Workflow	Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase
Complexity	advanced
Nodes	28
Categories	Invoice Processing, AI Summarization
Author	Kumar SmartFlow Craft
Published	18 Mar 2026

4. Reproducing the Workflow from Scratch

1. Download the workflow JSON

Use the JSON export at /data/workflows/14146/14146.json as the source template for this automation.
2. Import the template into n8n

Open n8n, import the downloaded JSON, and review each node before activating the workflow.
3. Configure credentials and variables

Replace placeholder credentials, API keys, webhook URLs, account IDs, and environment-specific values with your own settings.
4. Test with sample data

Run the workflow manually or in a staging workspace, inspect node output, and confirm downstream systems receive the expected data.
5. Activate and monitor

Enable the workflow only after testing, then monitor executions, errors, and rate limits during the first production runs.

5. General Notes & Resources

Review imported nodes carefully before activation. This catalog entry is intended to help you inspect the workflow structure, understand required services, and find related templates faster.

Node names, credentials, schedules, webhook paths, and external service limits may need adjustment for your workspace.

Download workflow JSON Original n8n.io source Invoice Processing workflows AI Summarization workflows

Frequently asked questions

What does Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase do?

How it works Monitors your AP inbox for incoming invoices, extracts structured data with AI, runs duplicate and vendor history checks against Supabase, then scores each invoice for fraud risk — ...

What do I need before importing this workflow?

Review the workflow JSON, configure any required credentials in n8n, and test the automation in a safe workspace before using it in production.

Can I customize this workflow?

Yes. Use the block-by-block analysis and the downloadable JSON to inspect each node, then adjust credentials, prompts, schedules, filters, or destinations for your Invoice Processing, AI Summarization use case.

Kumar SmartFlow Craft

6 workflows

Nodes

n8n-nodes-base.stickynote n8n-nodes-base.gmailtrigger @n8n/n8n-nodes-langchain.agent @n8n/n8n-nodes-langchain.lmchatopenai @n8n/n8n-nodes-langchain.outputparserstructured n8n-nodes-base.supabase n8n-nodes-base.code n8n-nodes-base.if

Complexity

advanced

Published 18 Mar 2026

Likes 0

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Install path: /data/workflows/14146/14146.json

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Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase

Workflow preview

1. Workflow Overview

Best for

Tools used

Source and attribution

1.1 Workflow description

🚀 How it works

🛠️ Set up steps

📋 Prerequisites

Custom Workflow Request with Personal Dashboard

More free templates

1.2 Logical Blocks

2. Block-by-Block Analysis

Block 1 - Overview

Block 2 - Prerequisites

Block 3 - Setup Required

Block 4 - How It Works

Block 5 - Gmail — Invoice Inbox

Block 6 - Extract note

Block 7 - Extract Invoice Data

Block 8 - OpenAI — Extract

Block 9 - Invoice Data Schema

Block 10 - Duplicates note

Block 11 - Check Duplicates

Block 12 - Count Dup note

Block 13 - Count Duplicates

Block 14 - Vendor note

Block 15 - Check Vendor History

Block 16 - Merge Context note

Block 17 - Merge All Context

Block 18 - Risk note

Block 19 - Assess Fraud Risk

Block 20 - OpenAI — Risk

Block 21 - Fraud Risk Schema

Block 22 - High Risk note

Block 23 - High Risk?

Block 24 - Slack note

3. Summary Table

4. Reproducing the Workflow from Scratch

1. Download the workflow JSON

2. Import the template into n8n

3. Configure credentials and variables

4. Test with sample data

5. Activate and monitor

5. General Notes & Resources

Frequently asked questions