As of 13 August 2026, AI can calculate mileage reimbursement for your employees.

What to actually do

1. Hand it to a person

   The route this page recommends

   A person who owns the outcome does this end to end, worth it when the failure is dear.

2. Use a tool built for this

   Second choice

3. Do it yourself

   The distant third

   A chat interface, chat-fluent skill, and roughly 30 minutes until you can act on the result.

   How to actually do it

   1. Open your current mileage policy and the relevant GOV.UK HMRC guidance, then copy the applicable rules and rates into separate sections.
   2. Export the mileage log from your expenses or payroll system and add the employee reference, journey date, business miles, vehicle type, eligibility status and any exceptions.
   3. Paste the policy, guidance, mileage log and the prompt into an AI chat, then ask it to calculate the claims without guessing missing information.
   4. Copy the AI's line-by-line results and CSV-style table into a spreadsheet, keeping the original mileage log in a separate sheet.
   5. Compare every journey, mileage figure and eligibility decision with the original records and compare the applied rates with the current GOV.UK guidance and your company policy.
   6. Ask a payroll colleague or accountant to resolve flagged exceptions and confirm the payroll treatment before sending the approved totals for payment.

   Prompt

   Calculate employee mileage reimbursement from the data and rules below.
   
   Use only the figures and rules I provide. Do not invent missing journeys, rates, vehicle types, passenger details or tax treatment. If anything needed is missing or contradictory, list it under 'Questions before calculation' instead of guessing.
   
   Business policy:
   [Paste the current company mileage reimbursement policy]
   
   Applicable HMRC guidance or rates:
   [Paste the relevant current GOV.UK guidance or the rates approved for this calculation]
   
   Mileage log:
   [Paste a table with employee name or ID, date, journey start, destination, business miles, vehicle type, whether the journey is eligible under the policy, and any passenger or exception details]
   
   Produce:
   1. A line-by-line calculation for every eligible journey.
   2. The reimbursement amount for each employee.
   3. Separate totals for eligible mileage, excluded mileage and any amount requiring manual review.
   4. A reconciliation showing the total of all employee amounts.
   5. A list of assumptions, missing information and possible policy or HMRC issues.
   6. A clean CSV-style table that I can paste into a spreadsheet.
   
   Keep reimbursement calculations separate from any tax or payroll conclusion. Do not state that a payment is tax-free unless that follows directly from the supplied policy and guidance. Show the formula used for every total and preserve the original employee and journey references.

   Open it prefilled in ChatGPT or Claude, or copy it into Gemini, which takes no prefill link.