Approve Employee Expenses with OpenAI, Google Sheets & Telegram

Approve employee expenses automatically—using OpenAI, Google Sheets, and Telegram

This n8n workflow receives employee expense submissions through a webhook, uses OpenAI (GPT-4o-mini) to categorize and determine whether manager approval is required, logs everything to Google Sheets, and keeps both employees and managers in sync via Telegram (plus follow-up approval requests by Gmail).

What this workflow does

• Receives submissions via POST webhook: Accepts expense fields such as employee_name, employee_chat_id, description, amount, currency, and vendor.
• Validates and normalizes data: Generates an expense ID, normalizes key fields, and rejects invalid submissions by notifying the employee in Telegram.
• Uses OpenAI to enrich each expense: Sends expense details to GPT-4o-mini to classify the category, clean the amount, and decide whether manager approval is needed.
• Logs to Google Sheets: Appends an enriched record into a Google Sheets “Expenses” sheet with AUTO_APPROVED or PENDING_APPROVAL status.
• Routes approvals:
  • If PENDING_APPROVAL, sends the details to the manager via Telegram and triggers an approval request email via Gmail.
  • If AUTO_APPROVED, notifies the employee via Telegram.
• Monthly summary report: On the 1st day of each month, reads logged expenses from Google Sheets, asks OpenAI to generate a monthly summary, and sends the report to the manager via Telegram.

Use cases

• Streamline reimbursements by auto-categorizing expenses and flagging exceptions for manager review.
• Centralize expense tracking in Google Sheets while maintaining real-time approvals through Telegram and Gmail.
• Generate consistent monthly expense reporting without manual spreadsheet work.

Technical details

• Integrations / nodes: Webhook, OpenAI (GPT-4o-mini), Google Sheets, Telegram, Gmail, plus workflow logic nodes like if and set.
• Output: Enriched “Expenses” rows with approval status and OpenAI-generated categorization.