n8n Mileage Reimbursement Report: Google Calendar + OpenAI + Dropbox

Turn Google Calendar trips into an accountant-ready mileage reimbursement Excel—automatically

This n8n workflow converts monthly Google Calendar trip events into a structured mileage reimbursement report in Excel (XLSX). It uses OpenAI to extract trip details from free-text events, OpenStreetMap (Nominatim) and OSRM to compute driving distances, then uploads the file to Dropbox. In live mode, it also prepares a Gmail draft with validation checks for your accountant.

What this workflow does

• Runs monthly on the 1st at 07:00 (or manually) and processes the previous month by default, with an optional manual month override.
• Pulls Google Calendar events for the target month and interprets trip information from titles formatted like “Departure > Arrival, km, purpose”.
• Handles multi-day travel by marking “Trasferta” events as away days.
• Sends remaining free-text trip events to OpenAI to extract: whether it’s a car trip, ordered stops, optional km, purpose, and whether it’s one-way or round-trip.
• If km is missing (or when verification is enabled), it geocodes stop names via OpenStreetMap Nominatim and calculates driving distance using OSRM routing.
• Builds a per-day reimbursement table, totals mileage, and flags issues such as km mismatches vs route, duplicate trips, excessive daily km, and AI-parsed trips that require review.
• Generates an XLSX report and uploads it to Dropbox.
• In live mode, records the processed month in an n8n Data Table to avoid duplicate drafting, then creates a Gmail draft with the Excel attached and emails an HTML summary.

Use cases

• Employees who log travel in Google Calendar and need a monthly mileage reimbursement package with computed driving distances.
• SaaS operators and automation engineers who want a reliable, auditable workflow combining AI parsing + routing validation.
• Teams that require accountant-friendly submission via Gmail drafts and a stored file in Dropbox.

Technical details

• Integrations / nodes: Google Calendar (OAuth2), OpenAI, Dropbox (OAuth2), Gmail (OAuth2).
• Logic & processing: if, set, code, filter, gmail, dropbox.
• Distance calculation: OpenStreetMap Nominatim + OSRM routing.