Extract invoice data from Slack PDFs to Google Sheets with GPT-4o

Managing invoices manually can be time-consuming and error-prone. This workflow automates the process by extracting key invoice details from PDFs shared in Slack, structuring the information with AI, saving it to Google Sheets, and sending a confirmation back to Slack. It’s a seamless way to keep your financial records organized without manual data entry.

How it works

1. Receive invoice in Slack – When a PDF invoice is uploaded to a designated Slack channel, the workflow is triggered.
2. Fetch the PDF – The file is downloaded automatically for processing.
3. Extract data from PDF – Basic text extraction is performed to capture invoice content.
4. AI-powered invoice parsing – An AI model interprets the extracted text and structures essential fields such as company name, invoice number, total amount, invoice date, and due date.
5. Save to Google Sheets – The structured invoice data is appended as a new row in a Google Sheet for easy tracking and reporting.
6. Slack confirmation – A summary of the saved invoice details is sent back to Slack to notify the team.

How to use

1. Import the workflow into your n8n instance.
2. Connect Slack – Authenticate your Slack account and set up the trigger channel where invoices will be uploaded.
3. Connect Google Sheets – Authenticate with Google Sheets and specify the target spreadsheet and sheet name.
4. Configure the AI extraction – Adjust the parsing prompt or output structure to fit your preferred data fields (e.g., vendor name, invoice ID, amount, dates).
5. Test the workflow – Upload a sample invoice PDF in Slack and verify that the data is correctly extracted and saved to Google Sheets.

Requirements

• An n8n instance (cloud)
• Slack account with permission to read uploaded files and post messages
• Google account with access to the spreadsheet you want to update
• AI integration (e.g., OpenAI GPT or another LLM with PDF parsing capabilities)
• A designated Slack channel for receiving invoice PDFs