As of 13 August 2026, AI can calculate your HMRC mileage allowance.

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, no skill needed, and roughly 15 minutes until you can act on the result.

   How to actually do it

   1. Open the current HMRC mileage guidance on GOV.UK and keep it beside your calculation.
   2. Gather your mileage record, tax year, vehicle details, business miles, qualifying passenger journeys and any amounts your employer has already paid.
   3. Paste the prompt and your records into a chatbot, then ask it to separate employer reimbursement from any possible tax relief.
   4. Compare every rate, mileage band and eligibility rule in the answer with the current GOV.UK guidance, replacing any unsupported value before accepting the result.
   5. Recalculate the totals from the table using a calculator or spreadsheet and resolve every missing or flagged input from your mileage records.
   6. Send the checked figure and supporting mileage record to your employer or payroll team, and keep the source guidance and calculation with your expense records.

   Prompt

   Calculate my UK HMRC mileage allowance from the information below. First identify whether I am asking for an employer mileage payment, tax relief on unreimbursed business mileage, or both. Use only the current HMRC guidance at https://www.gov.uk/expenses-and-benefits-business-travel-mileage and do not rely on remembered rates. If you cannot access or verify the current GOV.UK guidance, say so and do not invent a rate. Show the applicable rate, the mileage bands or thresholds used, the calculation for each vehicle or mileage category, any passenger-related amount, amounts already reimbursed, and the remaining amount separately. Do not include commuting or private miles. Flag missing, inconsistent or ambiguous inputs instead of guessing. Give the result in pounds, show the arithmetic in a table, and finish with a short list of checks I must make before submitting the claim.
   
   Tax year: [insert tax year]
   Vehicle type and fuel: [insert details]
   Total business miles by vehicle or mileage category: [insert figures]
   Business miles already reimbursed by my employer: [insert figures]
   Qualifying passenger journeys and passenger details: [insert details or none]
   Any other relevant mileage payments or reimbursements: [insert details or none]
   Employer policy or expense rules: [paste relevant wording]
   Mileage record or journey list: [paste record]

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