Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase β€” n8n Workflow

Medium complexity⚑ Trigger15 nodes🏷️ Invoice Processingby Kumar SmartFlow Craft

Overview

πŸš€ 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 β€” routing suspicious ones to Slack and your AP team before any payment is processed.

πŸ“¬ Gmail Trigger monitors your accounts payable inbox in real time πŸ€– AI Agent extracts invoice number, vendor, amount, currency, dates and line items into structured JSON β€” no manual data entry πŸ” Checks

Nodes used

SlackGmailSupabaseCodeAI AgentOpenAI Chat ModelStructured Output Parser

Workflow Preview

AP Invoice Fraud Detection
Version 1.0.0 β€” Finance
Processes incoming invoices from Gmail, extracts struct
Prerequisites
- Gmail account receiving invoices (Gmail OAuth2 creden
- OpenAI API key (GPT-4o)
- Supabase project with two tables:
- invoices: invoice_number, vendor_name, amount, stat
Setup Required
1. Gmail Trigger β€” connect Gmail OAuth2 credential
2. Extract Invoice Data β€” connect OpenAI credential
3. Check Duplicates + Check Vendor History β€” connect Su
How It Works
1. Gmail Trigger detects new invoice emails (attach PDF
2. AI Agent extracts: invoice number, vendor, amount, i
3.
AI extracts structured invoice data from emai
Queries invoices table for existing records w
Consolidates duplicate rows into a single ite
Queries vendor history to detect unusual amou
Merges invoice data, duplicate count, and ven
AI Agent scores fraud risk using duplicate co
Routes to Slack alert path if risk requires h
Posts fraud alert to #invoice-alerts Slack ch
Logs every processed invoice to Supabase for
modelparsermodelparser
⚑
G
Gmail β€” Invoice Inbox
Extract Invoice Data
OpenAI β€” Extract
Invoice Data Schema
Check Duplicates
Count Duplicates
Check Vendor History
Merge All Context
Assess Fraud Risk
OpenAI β€” Risk
Fraud Risk Schema
H
High Risk?
Alert Slack
Send Hold Notice
Log Invoice to Supabase
15 nodes15 edges

How it Works

  1. 1

    Trigger

    The workflow starts with a trigger trigger.

  2. 2

    Process

    Data flows through 15 nodes, connecting agent, code, gmail.

  3. 3

    Output

    The workflow completes its automation and delivers the result to the configured destination.

Node Details (15)

SL

Slack

slack

#1
GM

Gmail

gmail

#2
SU

Supabase

supabase

#3
CO

Code

code

#4
AI

AI Agent

n8n-nodes-langchain.agent

#5
OP

OpenAI Chat Model

n8n-nodes-langchain.lmChatOpenAi

#6
ST

Structured Output Parser

n8n-nodes-langchain.outputParserStructured

#7

How to Import This Workflow

  1. 1Click Download JSON button on the right to save the workflow file.
  2. 2Open your n8n instance. Go to Workflows β†’ New β†’ Import from file.
  3. 3Select the downloaded flag-duplicate-and-risky-ap-invoices-with-gmail-openai-and-supabase file and click Import.
  4. 4Set up credentials for each service node (API keys, OAuth, etc.).
  5. 5Click Test Workflow to verify everything works, then activate it.

Or paste directly in n8n β†’ Import from JSON:

{ "name": "Flag duplicate and risky AP invoices with Gmail, OpenAI and Supabase", "nodes": [...], ...}

Integrations

agentcodegmailgmailtriggeriflmchatopenaioutputparserstructuredslacksupabase

Get This Workflow

Download and import in one click

Download JSONView on n8n.io
Nodes15
Complexitymedium
Triggertrigger
CategoryInvoice Processing

Created by

Kumar SmartFlow Craft

Kumar SmartFlow Craft

@smartflowautomate

Tags

agentcodegmailgmailtriggeriflmchatopenaioutputparserstructuredslacksupabase
⚑

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Standard accounting templates often fail to reflect a premium brand identity. This sophisticated n8n workflow bridges the gap between financial record-keeping and professional client presentation. By moving beyond the native limitations of QuickBooks Online, this automation enables businesses to generate high-end, multi-page PDF invoices that align perfectly with their corporate styling. The process begins the moment a new invoice is generated in QuickBooks, triggering a webhook that captures real-time billing data. The workflow then utilizes advanced HTML-to-File conversion and custom Code nodes to structure data into a polished, branded layout. It handles complex logic such as line-item merging and multi-page formatting automatically. Once the document is rendered, the system bypasses generic 'no-reply' senders by routing the finalized PDF through your preferred email provider. This ensures a seamless, white-labeled experience for your clients while eliminating the manual overhead of exporting, styling, and attaching files. Ideal for agencies and service providers, this flow guarantees that your most frequent touchpointβ€”the billβ€”is as professional as your work. **Common Use Cases:** - High-end creative agencies requiring bespoke, white-labeled billing documents for premium clients. - Automated recurring subscription billing where custom tax disclosures or localized branding are required. - Service-based businesses needing to attach dynamic project reports or terms of service directly to QuickBooks invoices.

πŸ”— WebhookΒ·12 nodes