Track and classify expenses with Mindee OCR, GPT-4o, PostgreSQL and Google Drive

Quick overview

This workflow collects receipt uploads via an n8n form, extracts expense details with Mindee OCR, enriches and classifies the expense using OpenAI, stores the receipt in Google Drive, saves the final record to PostgreSQL, and sends Slack alerts plus a daily analytics summary.

How it works

1. Receives an expense submission through an n8n form with a receipt file and optional amount and notes.
2. Validates that the receipt file exists, then uploads the file to Google Drive and enqueues it for OCR processing in Mindee.
3. Polls Mindee for the OCR result, extracts key fields (merchant, amount, date, category, receipt number, and raw text), and alerts in Slack if OCR fails.
4. Checks that required fields (merchant and amount) were extracted and sends a Slack alert for manual review when the receipt data is incomplete.
5. Sends the extracted receipt data to OpenAI to classify the expense (final category, business vs personal, expense type, and confidence), then blocks low-confidence results.
6. Combines the OCR data, AI classification, and Google Drive receipt URL, checks PostgreSQL for duplicates by receipt number and amount, and either alerts in Slack or inserts the expense record into PostgreSQL and posts a success message.
7. Runs daily on a schedule to query PostgreSQL for spending analytics and posts a dashboard-style summary to Slack.

Setup

1. Create and connect credentials for Mindee (HTTP header auth), OpenAI, Slack, Google Drive OAuth, and a PostgreSQL database.
2. Create a PostgreSQL expenses table with columns used by the insert (amount, user_id, merchant, currency, expense_date, category, subcategory, ai_category, business_or_personal, expense_type, confidence, receipt_number, raw_text, receipt_url).
3. Set the Google Drive folder destination for uploads and ensure the workflow has permission to write to that folder.
4. Update the Slack channel selections for failure/duplicate alerts and for successful processing and daily dashboard messages.
5. If needed, adjust the Mindee model_id and the daily schedule time to match your OCR model and reporting cadence.

Additional info

Use Case Examples

1. Employee Expense Automation

Employees upload receipts and finance teams automatically receive categorized expense records without manual entry.

2. Freelancer Expense Tracking

Freelancers can automatically organize personal and business expenses for tax preparation.

3. Startup Finance Operations

Startups can centralize expense management, receipt storage, and spending analytics in a single workflow.

4. AI-Powered Bookkeeping

Accounting teams can reduce manual categorization using AI-based expense classification.

5. Expense Audit & Compliance

Organizations can maintain secure receipt archives with searchable OCR text and structured database records.

Additional use cases can include:

• reimbursement systems,
• travel expense management,
• procurement monitoring,
• finance analytics automation,
• and AI-driven expense intelligence platforms.

Troubleshooting Guide

Issue	Possible Cause	Solution
OCR extraction fails	Invalid Mindee API credentials	Verify API key and HTTP Header Auth configuration
Receipt upload fails	Unsupported file type or missing binary data	Ensure the form uploads valid image or PDF files
AI classification fails	Invalid OpenAI credentials or malformed JSON response	Verify API credentials and AI response parsing
Expense not saved	PostgreSQL connection issue	Check database credentials and table schema
Duplicate expenses not detected	Missing receipt number or amount	Improve OCR extraction or modify duplicate query
Google Drive upload fails	OAuth permissions issue	Reconnect Google Drive credentials
Slack alerts not sent	Invalid Slack credentials or channel configuration	Reconfigure Slack API integration
Analytics dashboard empty	No expense records in database	Ensure expenses are successfully inserted
Workflow stops unexpectedly	OCR validation failure	Review Slack alerts and node execution logs
Confidence score too low	Poor OCR quality or unclear receipt image	Upload higher-quality receipt images

Need Help?

If you need help with:

• workflow setup,
• PostgreSQL configuration,
• AI integrations,
• OCR customization,
• analytics dashboards,
• approval systems,
• or advanced automation features,

our n8n development team at WeblineIndia can help you customize and scale this workflow according to your business requirements.

Whether you want:

• custom AI workflows,
• enterprise automation,
• finance process automation,
• or intelligent document processing systems,

this workflow can be extended into a complete production-ready expense management platform.