Gmail + Google Drive AP Invoice Automation with Gemini & QuickBooks

Automatically turn Gmail + Google Drive invoice attachments into QuickBooks Online vendor bills—using Gemini, confidence checks, and Slack review

This n8n workflow watches your Gmail and a Google Drive folder for new invoice documents, extracts invoice data with Google Gemini, and then either creates QuickBooks Online vendor bills or routes uncertain invoices to a finance reviewer in Slack.

What this workflow does

• Monitors for new invoices every minute: triggers when an unread Gmail message with an invoice attachment arrives or when a new file is created in a specified Google Drive folder.
• Normalizes and downloads the document: processes attachment/file metadata and downloads the file from Google Drive when needed.
• Extracts content by MIME type: pulls embedded text from PDFs; when the document is an image (including scanned PDFs with no extracted text), it sends the file to Google Gemini vision for analysis.
• Extracts structured invoice fields with Gemini (e.g., vendor, invoice dates, totals, line items, and payment details) and normalizes the result into a consistent invoice JSON payload.
• Validates confidence scores using a 0.9 confidence threshold for key fields: vendor name, invoice number, and total amount.
• Routes outcomes:
  • High confidence: appends to Google Sheets “Invoices_Raw” and creates a vendor bill in QuickBooks Online.
  • Low confidence: appends to Google Sheets “Invoices_Exceptions” and sends a Slack message to the finance reviewer with key details and confidence scores for manual review.

Use cases

• Accounts payable teams receiving invoices via email while also archiving copies to Google Drive.
• Automation engineers building an invoice ingestion pipeline that uses Gemini for extraction and human-in-the-loop verification in Slack.
• SaaS operators who need faster QuickBooks Online bill creation with audit-friendly logging in Google Sheets.

Technical details

• n8n trigger logic: periodic execution (every minute) with rules around unread Gmail messages and new Drive files.
• Integrations/nodes mentioned: Gmail, Google Drive, Google Sheets, Slack (OAuth2), Google Gemini, plus workflow control via if, switch, and code nodes.
• Workflow routing: if conditions + switch for MIME-type extraction handling; results logged to the two Google Sheets tabs based on confidence.