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

Description

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

How to set up
Create a Google Sheet with columns like:

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

Connect:
Google Sheets OAuth
Google Gemini (PaLM API key) for LLM parsing
Deploy the webhook endpoint: /uploadDoc
Upload sample files (PDFs, images, CSVs) to test
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.