Mileage Claim HMRC: Self-Employed Workflow That Survives Review

Most HMRC mileage claim problems are not about getting the maths wrong. They come from weak evidence, inconsistent classification, and filing everything in a panic the week before the Self Assessment deadline.

This guide sets out a repeatable workflow for self-employed people who want cleaner claims and less stress at year-end.

Simplified expenses vs actual cost method

Before you start tracking, you need to pick your approach. HMRC gives self-employed people two ways to claim vehicle costs.

Simplified expenses (flat rate)

Use HMRC’s Approved Mileage Allowance Payment rates:

• 45p per mile for the first 10,000 business miles
• 25p per mile after that

This flat rate covers fuel, insurance, repairs, servicing, road tax, and depreciation. You do not claim any of those costs separately — the rate is meant to cover everything.

The simplified method is easier to administer. You track business miles, multiply by the rate, and enter the total on your tax return.

Actual cost method

Track every vehicle expense: fuel, insurance, MOT, servicing, repairs, breakdown cover, road tax, financing costs, and depreciation (or lease payments). At year-end, calculate the percentage of total miles that were for business, and apply that percentage to your total costs.

For example, if you drove 15,000 miles total and 9,000 were business, your business-use percentage is 60%. If your annual vehicle costs were £4,800, you claim £2,880.

The lock-in rule

Once you use the actual cost method for a vehicle, you cannot switch back to simplified expenses for that same vehicle. You can still use simplified expenses for a different vehicle. HMRC’s simplified expenses guidance explains the rules.

For most self-employed people who drive moderate distances, simplified expenses are simpler and often more generous. The actual cost method tends to benefit those with low running costs or very high mileage.

Build a claim policy before you start tracking

Write down a short internal policy for yourself:

• What counts as business travel in your trade? (Client visits, supplier trips, training, temporary workplaces.)
• What is ordinary commuting? (Travel to your one regular place of work — not claimable.)
• How do you handle mixed-purpose days? (If you combine a client visit with a personal errand, only the business leg counts.)

Having this written down, even informally, keeps your classification consistent across the year.

Weekly journey review

Every week, spend five to ten minutes on your mileage records:

• Open uncategorised journeys.
• Classify each as business or personal.
• Add a short purpose note: “Site visit to Jenkins Construction, Leeds” rather than just “work.”
• Fix any obvious route errors (GPS drift, duplicate entries).

Weekly is better than monthly. After four weeks, you will struggle to remember whether a Tuesday trip to Birmingham was a client meeting or a personal errand.

Month-close evidence pack

At month-end, produce a small archive:

1. Monthly summary — total business miles, total personal miles, cumulative annual business miles, and the AMAP amount for that month.
2. Raw journey export — every recorded trip with date, origin, destination, purpose, and miles.
3. Supporting documents (optional) — receipts or invoices linked to specific journeys.

A folder structure like mileage/2026/04/ keeps things tidy. Consistent monthly packaging makes life far easier when your accountant asks for “the March figures.”

Where the claim goes on your tax return

Self-employed mileage claims go on the SA103 supplementary pages (self-employment). If you use simplified expenses, enter the flat-rate amount in the expenses section. If you use actual costs, enter the business proportion of your vehicle expenses.

You report business mileage separately from other motor expenses. The GOV.UK Self Assessment page has the current filing guidance and deadlines.

Threshold-aware calculation

Track cumulative yearly miles so the AMAP threshold is applied correctly:

• First 10,000 business miles at 45p = up to £4,500
• Every mile after that at 25p

If your annual mileage is high, getting this split wrong costs real money. Someone who drives 14,000 business miles and applies 45p to all of them would claim £6,300. The correct figure is £5,500 — a £800 overstatement that HMRC’s systems can flag automatically.

Record retention

HMRC requires self-employed people to keep business records for at least five years after the 31 January Self Assessment deadline for the relevant tax year. For the 2025/26 tax year (deadline 31 January 2027), that means holding onto your mileage records until at least 31 January 2032.

This applies to everything: monthly exports, raw journey data, receipts, and any supporting correspondence. If you switch tracking apps during that period, make sure you export and archive your data before closing the old account. The GOV.UK self-employed records page confirms the retention requirements.

Choosing between simplified and actual: a quick comparison

If you are unsure which method suits you, run both calculations for a single tax year:

• Simplified: Total business miles × AMAP rate (45p/25p split at 10,000 miles).
• Actual: Total vehicle costs × business-use percentage.

For someone driving 8,000 business miles with annual vehicle costs of £3,200 and 70% business use, simplified expenses give £3,600 (8,000 × 45p) while actual costs give £2,240 (£3,200 × 70%). Simplified wins clearly in that scenario.

The actual cost method tends to come out ahead only when vehicle costs are very high relative to mileage — for instance, a new van with heavy finance payments and low annual mileage.

Remember the lock-in: once you choose actual costs for a vehicle, there is no going back to simplified for that same vehicle.

High-risk scenarios to watch

Multiple workplaces

If you alternate between home, a shared office, and client sites, annotate workplace context on every trip. Ordinary commuting to your main business premises is not claimable. Travel between workplaces usually is. HMRC looks at the pattern — if you drive to the same address five days a week and call it a “temporary workplace,” that will not hold up.

Multi-stop days

Break journey chains into logical segments. A route that goes Home → Client A → Supermarket → Client B has a personal leg in the middle. Record each segment separately so the personal miles are clearly excluded.

Late reconstruction

If you missed a few weeks of tracking, reconstruct using your calendar, invoices, and Google Maps timeline. Mark those entries as reconstructed. HMRC will not reject reconstructed records outright, but they carry less weight than contemporaneous logs. The further back you go, the weaker the evidence becomes.

What to store for HMRC confidence

Your records should make each claim understandable to someone who knows nothing about your business:

• Date of journey
• Start and end locations (specific — include the town and the business name or site)
• Business purpose (why you went, not just “work”)
• Miles driven (measured, not estimated)
• Vehicle used

Supporting evidence strengthens your position. Calendar entries, client invoices dated the same day as a journey, or email confirmations of meetings all corroborate your log without needing to be formally attached to each entry.

For rate-specific details, see HMRC Mileage Rates 2026: Practical AMAP Guide for UK Claims. For logging structure, read HMRC Mileage Logbook Rules: Recordkeeping Checklist for 2026.

Tool selection criteria

Choose mileage tracking software that supports the specific needs of UK self-employed filers:

• Quick corrections and reclassification of journeys.
• Clear business-purpose tagging with free-text notes.
• Annual mileage threshold awareness (the 10,000-mile AMAP split).
• Stable month-by-month exports in PDF and CSV formats.

These features matter more than GPS animation or social sharing. The test is whether the app produces exports that your accountant can work with and HMRC would accept.

Final submission checklist

Before filing your Self Assessment:

• Reconcile annual totals from monthly exports.
• Confirm the 10,000-mile threshold split is correct.
• Verify commuting treatment is consistent — no permanent-workplace trips classified as business.
• Check that no uncategorised journeys remain.
• Keep all records accessible for at least five years after the 31 January filing deadline.

A mileage claim that follows this workflow is a repeatable monthly process, not a January scramble.

MileTrack captures journeys automatically, classifies them as business, commute, or private, and exports claim-ready reports with all the fields HMRC expects. See the current UK product page at miletrack.app/en-gb.

Tax note: this article is educational and does not replace advice from a qualified UK tax professional.