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Split shared rental utility bills with GPT-4o Vision, Postgres and Gmail

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Created by: Khairul Muhtadin || khmuhtadin
Khairul Muhtadin

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Last update a day ago

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Quick Overview

This workflow accepts forwarded utility bill images via a webhook, uses OpenAI gpt-5.6-terra Vision to extract bill details, splits the total across rental units using Postgres tenant weights, and then notifies owners and tenants via Gmail and Discord, with daily follow-ups for any bills not completed.

How it works

  1. Receives a POST webhook request containing a utility bill image (URL or base64) and basic metadata from an email forward or form.
  2. If an image is present, sends it to OpenAI gpt-5.6-terra Vision and parses the returned JSON fields such as provider, dates, period, and total amount.
  3. Rejects unreadable bills, missing totals, or non-positive totals by logging them to Postgres and alerting the team via Discord and Gmail.
  4. For valid bills, loads the tenant roster from Postgres and calculates a deterministic per-unit charge split proportional to each unit’s occupancy weight with cent-accurate rounding.
  5. Stores the bill and per-unit charge records in Postgres, posts a split summary to Discord, emails the owner a detailed breakdown, and emails each tenant their individual charge.
  6. Marks the bill as done in Postgres after tenant notifications are sent.
  7. Runs daily on a schedule to find older bills not marked done in Postgres and posts/email a follow-up list (or an all-clear) to Discord and the owner.

Setup

  1. Add credentials for OpenAI (API key), Postgres, Gmail OAuth2, and a Discord bot, and ensure the Discord server/channel IDs match your workspace.
  2. Create the Postgres tables used by the workflow (ub_tenants, ub_bills, and ub_meter_readings) and ensure ub_bills has a unique constraint on bill_id.
  3. Populate ub_tenants with each unit’s tenant name, email, and occupancy_weight values used to split bills.
  4. Update the owner notification email address in the Gmail steps and confirm tenant emails in ub_tenants are correct.
  5. Copy the webhook URL for the “utilitybill” endpoint and configure your email forwarding rule or intake form to POST the image_url or image_base64 fields to it.
  6. Adjust the daily sweep cron expression (default 08:00) and workflow timezone if needed.

Additional info

Built with n8n. Need an assessment on your business? Feel free to reach out at https://khmuhtadin.com/consultation/