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 Receive invoice in Slack – When a PDF invoice is uploaded to a designated Slack channel, the workflow is triggered. Fetch the PDF – The file is downloaded automatically for processing. Extract data from PDF – Basic text extraction is performed to capture invoice content. 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. Save to Google Sheets – The structured invoice data is appended as a new row in a Google Sheet for easy tracking and reporting. Slack confirmation – A summary of the saved invoice details is sent back to Slack to notify the team.

How to use Import the workflow into your n8n instance. Connect Slack – Authenticate your Slack account and set up the trigger channel where invoices will be uploaded. Connect Google Sheets – Authenticate with Google Sheets and specify the target spreadsheet and sheet name. 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). 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