n8n Workflow: Invoice OCR to Google Sheets Margin Pricing

Turn Supplier Invoices into Margin-Safe Menu Prices (Automatically)

This n8n workflow watches a Google Drive folder for new supplier invoice images, uses OpenAI GPT-4o Vision to extract normalized ingredient unit prices, stores them in Google Sheets, and then runs a weekly margin check to email the owner recommended menu price adjustments via Gmail.

What this workflow does

• Invoice ingestion from Google Drive: When a new invoice file is created in a specified Drive folder, the workflow downloads the image.
• Invoice OCR with OpenAI GPT-4o: The image is sent to OpenAI GPT-4o (Vision) to extract supplier details, invoice metadata, and per-ingredient unit prices (kg/l/each) as structured JSON.
• Normalize & record in Google Sheets: The extracted JSON is parsed into one row per invoice line and appended to an Ingredient Prices tab.
• Weekly margin monitoring (Mondays 8 AM): Every week, it reads POS Sales, Recipe Costing, and Ingredient Prices from Google Sheets.
• Detect margin drops & recommend pricing: It calculates current vs a 30-day baseline plate cost and identifies dishes where gross margin drops by at least 2 points. It flags the ingredient driving the increase, estimates the last-7-days profit leak, and generates a capped (+10%) rounded price suggestion.
• Owner-ready reporting: Flagged dishes are logged to a Margin Alerts tab, and gpt-4o-mini drafts a short owner-friendly summary.
• Email the pricing report: The workflow sends the weekly update to the owner using Gmail.

Use cases

• Restaurants and food operators who want automated invoice OCR and margin-based menu price recommendations.
• SaaS operators or automation engineers building a reliable Google Sheets costing + POS reporting pipeline in n8n.
• Teams who need weekly alerts when ingredient costs shift and margins erode.

Technical details

• Triggers: Google Drive new file created event
• Integrations: OpenAI (GPT-4o Vision + gpt-4o-mini), Google Drive, Google Sheets, Gmail
• n8n nodes used (from workflow): code, gmail, split out, sticky note, google drive, google sheets
• Scheduling: Weekly run every Monday at 8 AM