Extract Invoice Data from PDFs with AI and Log to Google Sheets with Email Alerts

Built by Setidure Technologies

This smart n8n automation extracts invoice details from PDF files uploaded to Google Drive using AI, logs them to a Google Sheet, and notifies the billing team via email — all without manual intervention.

⚠️ Note: This workflow requires a self-hosted n8n instance with LangChain, LLM, and Google integrations configured.

📦 What This Workflow Does

• Monitors a Google Drive folder for new invoice uploads
• Extracts text and parses key invoice details using LLM via LangChain
• Logs extracted data into a Google Sheet (Invoice Database)
• Generates a summary email using GPT-4O-MINI (Greenie)
• Sends the email to the billing team via Gmail

✅ Prerequisites

1. A Google Drive folder to monitor for PDF uploads
2. A Google Sheet named Invoice Database with the following columns:

• Invoice Number, Client Name, Client Email, Client Address, Client Phone, Invoice Date, Due Date, Total Amount

1. Service account or OAuth credentials for:

• Google Drive
• Google Sheets
• Gmail

1. LangChain + Ollama integration for LLM responses

🔧 Step-by-Step Setup Instructions

1. Clone this workflow into your self-hosted n8n instance
2. Set up credentials:

• Google Drive (for folder trigger)
• Google Sheets (for data logging)
• Gmail (for sending email)
• Ollama (local LLM) or any connected LangChain provider

1. Configure the trigger node to watch your specific Invoice Uploads folder
2. Update the Google Sheet node with your Invoice Database sheet URL and column mapping
3. Test with a sample invoice to validate the AI extraction and email generation

🔄 Workflow Steps

## Step 1: Trigger on New File in Google Drive

Node Name: Watch for New Invoices

Type: Google Drive Trigger

• Event: fileCreated
• Triggers when a new PDF file is uploaded to a designated folder

## Step 2: Download the Uploaded File

Node Name: Download Invoice PDF

Type: Download Binary

• Downloads the invoice file from Google Drive

## Step 3: Extract Raw Text from PDF

Node Name: Extract PDF Text

Type: Extract from File

• Extracts unstructured text content from the downloaded PDF

## Step 4: Parse Invoice Fields Using AI

Node Name: Parse Invoice Data with LLM

Type: LangChain Agent

• LLM is prompted to extract:
• Invoice Number
• Client Name, Email, Address, Phone
• Invoice Date, Due Date, Total Amount
• Fields not found are skipped

## Step 5: Log Extracted Data to Google Sheet

Node Name: Log to Invoice Database

Type: Google Sheets

• Appends a new row with the extracted fields to the Invoice Database spreadsheet

## Step 6: Create Email Notification via LLM

Node Name: Generate Billing Email Summary

Type: LangChain Agent (GPT-4O-MINI)

• Prompt instructs AI to:
• Act as “Greenie” from Green Grass Corp
• Inform billing that a new invoice was processed
• Confirm logging into the Invoice Database

## Step 7: Send the Email to Billing Team

Node Name: Email Billing Team

Type: Gmail Send

• To: billing@example.com
• Subject and body injected from LLM output

## Step 8: End Workflow Gracefully

Node Name: End

Type: No Operation

• Used to cleanly terminate the flow

🧠 Example Output (Email)

yaml

CopyEdit

Subject: New Invoice Logged – Client: ABC Corp

Hi Billing Team,

A new invoice has been received and processed automatically. The following details have been extracted and logged into the Invoice Database:

- Invoice Number: INV-1024

- Client: ABC Corp

- Amount: $1,450

- Due Date: July 15, 2025

Please review the [Invoice Database](https://docs.google.com/spreadsheets/d/14FtgVUjy0tw4EQOB2T8wuCYOe6CELtt3UTjn-GsuDWY/edit?gid=0#gid=0) for full details.

Regards,

Greenie

Green Grass Corp

📊 Flow Diagram (Mermaid)

mermaid

CopyEdit

flowchart TD

A[Google Drive Trigger: New File] --> B[Download Invoice PDF]

B --> C[Extract PDF Text]

C --> D[Parse Invoice Data with LLM]

D --> E[Log to Invoice Database]

E --> F[Generate Billing Email Summary]

F --> G[Email Billing Team]

G --> H[End]

📋 Suggested Node Name Replacements

Original Node NameSuggested NameExtract from FileExtract PDF TextInformation ExtractorParse Invoice Data with LLMSend EmailEmail Billing TeamOllama ModelGenerate Billing Email SummaryPostgres PGVector Store(Not used in this version)

🔐 Credentials Used

• Google Drive OAuth2 / Service Account
• Google Sheets OAuth2
• Gmail OAuth2
• Ollama API (Local LLM for prompt execution and embeddings)

🧾 License

Open source | Editable | Commercial use allowed