GPT-4o Vision Utility Bill Splitter | n8n Webhook + Postgres + Gmail

Split Utility Bills Automatically with GPT-4o Vision (n8n Webhook + Postgres + Gmail)

Send a utility bill image to an n8n webhook and this workflow will automatically extract key fields using GPT-4o Vision, split the total across your rental units using Postgres tenant weights, and notify both owners and tenants via Gmail—with daily follow-ups until every bill is completed.

What this workflow does

• Receives bill submissions via webhook: Accepts a POST request containing a utility bill image (URL or base64) plus basic metadata.
• Extracts bill details using GPT-4o Vision: If an image is present, the workflow parses returned JSON fields such as provider, dates/period, and total amount.
• Validates and handles errors: Rejects unreadable bills, missing totals, or non-positive totals—logging issues to Postgres and alerting the team via Discord and Gmail.
• Calculates per-unit charges: Loads the tenant roster from Postgres and computes a deterministic split proportional to each unit’s occupancy weight, using cent-accurate rounding.
• Saves records and communicates: Stores the bill and per-unit charge records in Postgres, posts a summary to Discord, emails the owner a detailed breakdown, and emails each tenant their individual charge.
• Marks completion: Updates the bill status as “done” in Postgres after tenant notifications are sent.
• Runs daily for follow-ups: Scheduled execution finds older bills not marked done and emails/posts a follow-up list (or an all-clear) to Discord and the owner.

Use cases

• Property managers splitting monthly utilities across multiple rental units without manual spreadsheets.
• Teams needing reliable bill extraction from forwarded email images or form uploads.
• Operators who want automated reminders for incomplete bill processing.

Technical details

• n8n nodes/tools: webhook, if, set, code, Gmail, Discord.
• Integrations: OpenAI GPT-4o Vision for extraction, Postgres for tenant roster + bill/charge storage, Gmail OAuth2 for notifications, and a Discord bot for alerts.
• Required setup: Configure credentials for OpenAI, Postgres, Gmail, and Discord, and ensure Discord server/channel IDs match your workflow settings.