n8n Leave Request Automation: Google Sheets, Gmail & Gemini

Automate employee leave requests end-to-end with n8n—Google Sheets tracking, Gmail approvals, and Gemini-crafted manager emails

This n8n workflow automatically captures leave requests from an n8n Form, checks leave balances in Google Sheets, and routes approvals via Gmail. When a manager needs to approve, Google Gemini drafts the approval email—and the workflow updates both the request status and balances in Sheets based on the manager’s email reply.

What this workflow does

• Collects submissions from an n8n Form, including employee, manager, date range, leave type, and reason.
• Validates leave balance by looking up the employee in the Google Sheets “Employee Data” spreadsheet and calculating requested days.
• Rejects early when needed: if balance is insufficient, sends a rejection email to the employee using Gmail.
• Requests approval when eligible: if balance is sufficient, uses Google Gemini to generate a manager approval email and sends it to the manager via Gmail.
• Creates/updates tracking in the “Leave Requests” Google Sheets spreadsheet with a generated request ID, status set to Pending, and the Gmail thread ID.
• Monitors manager decisions: polls Gmail for the manager’s reply, extracts APPROVED/REJECTED, matches the request by Gmail thread ID, and updates status in Google Sheets.
• Deducts leave on approval: when approved, subtracts the requested days from the employee’s leave balance in “Employee Data” by leave type.

Use cases

• HR or Ops teams managing leave approvals without manual spreadsheet updates.
• SaaS operators standardizing leave workflows across departments using n8n automation.
• Automation engineers building an email-based approval loop tied to Google Sheets records.

Technical details

• Google Sheets: “Employee Data” and “Leave Requests” lookups, writes, and balance updates.
• Gmail: sending employee/manager emails and using a Gmail Trigger to read manager replies.
• Google Gemini: generates the manager approval email message.
• n8n logic: nodes such as if, set, code, switch, and sticky note (plus workflow control for email-thread matching).

Setup requires connecting Gmail credentials for sending and the Gmail Trigger, then connecting Google Sheets credentials and configuring document/sheet IDs.