Parse Invoices & Documents with Gemini AI, OCR, and Google Sheets Integration

Smart Document Parser for Invoices, Logs or Sensor Reports (PDF/Image to Google Sheets)

This n8n workflow automatically parses documents such as invoices, sensor logs or structured PDFs/images (including scanned docs or CSVs), extracts key fields like totals, dates and customer/vendor info using OCR and AI, and writes the structured output into Google Sheets.

Who’s it for

• Finance or Ops teams automating invoice processing.
• SaaS platforms parsing uploaded reports or documents.
• Anyone needing a no-code backend for PDF/image/CSV document parsing.
• AI-powered data capture pipelines.

How it works

1. Webhook Trigger receives file uploads (/uploadDoc)
2. Switch Node checks the file type:
   • If image → Use Tesseract OCR
   • If PDF → Use PDF parser
   • If CSV → Extract as-is
3. Extracted text is passed to:
   • Google Gemini or Gemini Flash AI model
   • Prompt extracts fields like invoice_id, total, customer_name, etc.
4. JSON string is parsed and cleaned
5. Data is appended to Google Sheets using appendOrUpdate

How to set up

1. Create a Google Sheet with columns like:

invoice_id, invoice_date, due_date, customer_name, vendor_name, subtotal, tax_total, total, currency

1. Connect:
   • Google Sheets OAuth
   • Google Gemini (PaLM API key) for LLM parsing
2. Deploy the webhook endpoint: /uploadDoc
3. Upload sample files (PDFs, images, CSVs) to test
4. Review and map sheet columns in the Invoice Data node

Requirements

Tool

Purpose

n8n

Automation framework

Google Sheets

To store structured output

Tesseract OCR

For scanned image text extraction

Google Gemini

For natural language parsing

How to customize

• Add extraction for line items using structured prompts.
• Change prompt to extract sensor readings, log types, or custom keys.
• Add support for other file types (e.g., XLSX, DOCX).
• Add Slack/Email notifications on success/failure.
• Swap Gemini with OpenAI or Hugging Face if preferred.

Add‑ons

• Save uploaded files to Google Drive or S3
• Add auth for secure uploads
• Use charting/dashboard nodes to visualize extracted data
• Integrate with billing/accounting software

Use Case Examples

Scenario

What Happens

Invoice Upload (PDF)

Extracts totals, customer, tax data into a Google Sheet

Scanned Receipt (Image)

OCR + LLM extracts structured data

Log File (CSV)

Parses and logs entries into Sheets

Common troubleshooting

Issue

Possible Cause

Solution

Webhook not triggered

URL or method mismatch

Use correct POST URL /uploadDoc

Text is blank

OCR failed

Check image quality or Tesseract config

Gemini model not returning JSON

Prompt formatting issue

Ensure prompt ends with valid JSON schema

Sheet not updated

Invalid Sheet ID or tab

Double-check sheet credentials and tab name

Need Help?

• Need help fine-tuning the Gemini prompt for better field accuracy?
• Want to extract full tables, multi-page invoices or convert PDFs to JSON lines?

Our automation team at WeblineIndia can help you extend this into a full-blown document automation pipeline.