Collect mileage claims from travelers including trip date, origin address, and destination address; validate addresses before submission to reduce geocoding failures downstream
Call the Google Maps Routes API computeRouteMatrix endpoint with the claimed origin and destination to obtain the driving distance in meters; convert to miles by dividing by 1,609.344
Apply the IRS standard business mileage rate for the year of the trip: 70 cents per mile for trips in 2025 and 72.5 cents per mile for trips in 2026 per IRS Notice 2026-10
Compute the reimbursable amount and compare it to any amount the traveler claimed; flag discrepancies above a configurable tolerance for manager review
Store the computed route distance and IRS rate version used in the claim record to create an audit trail demonstrating the calculation method
Export approved reimbursements to your expense platform or payroll system with the mileage, rate, and computed amount as separate line-item fields for tax reporting purposes
Known gotchas
IRS mileage rates are updated annually and sometimes mid-year; hardcoding a rate value rather than storing it in a configuration table will cause incorrect calculations in the year following a rate change
Google Routes API computes the algorithmically optimal driving route, which may differ from the route actually driven; the IRS permits reimbursement for actual reasonable routes, so the API distance is a verification tool, not an absolute limit
Commuting miles between home and a regular workplace are not reimbursable under IRS rules; validate trip origin against the employee's registered home and office addresses to detect commute-disguised-as-business claims
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp