Claiming Mileage on Self Assessment: 2025/26 Filing Checklist

Updated 2 October 2026: this guide covers trips in the UK 2025/26 tax year and the 31 January 2027 online filing deadline. The 55p increase applies to 2026/27, not this earlier return.

Quick Answer: Prepare Your 2025/26 Mileage Claim

For a 2025/26 Self Assessment mileage claim, review trips dated 6 April 2025 to 5 April 2026. The standard online filing and payment deadline is 31 January 2027. Keep later journeys out of that return.

Use this order:

1. Backfill missing business trips.
2. Remove personal or non-allowable travel.
3. Confirm your claim method (simplified mileage rate or actual vehicle costs).
4. Save evidence for business purpose.
5. Export and lock your year-end mileage summary.

For the 2025/26 tax year, filing opened on 6 April 2026, and the standard online filing and payment deadline is 31 January 2027.

Start cleaning up your mileage log in DriveLog.

Keep 2025/26 and 2026/27 Rates Separate

• 2025/26: cars and vans use 45p for the first 10,000 business miles, then 25p.
• 2026/27: the first-tier rate is 55p, then 25p, effective 6 April 2026. The increase was announced on 21 May and backdated to the start of that tax year.
• Filing a 2025/26 return in January 2027 does not entitle you to use 55p for those earlier trips.

For example, 8,000 qualifying car miles in 2025/26 give a £3,600 simplified mileage expense (8,000 × £0.45). The same distance in 2026/27 gives £4,400 (8,000 × £0.55), assuming eligibility in each year.

Source: HMRC simplified vehicle expenses. See the full HMRC rate guide and how to handle the 55p increase for current-year claims.

Key Dates for the 2025/26 Tax Year

Milestone	Date	Why it matters
Tax year ends	5 April 2026	Cutoff point for trips you include in 2025/26 totals
New filing window opens	6 April 2026	Filing opens for the completed 2025/26 tax year
Register if newly required to file	5 October 2026	HMRC registration trigger date for many first-time filers
Online filing and payment deadline	31 January 2027	Main Self Assessment submit and pay deadline

If you use payments on account, keep the July instalment cycle in mind as part of cash planning.

Can You Claim Mileage on Self Assessment?

For sole traders and many partnerships, yes, but only for allowable business travel.

HMRC generally does not allow ordinary commuting (home to a permanent workplace) as business mileage. Your records should show business purpose clearly enough that each trip can be explained later.

Method choice matters

You normally use one of these approaches:

1. Simplified expenses mileage rates for eligible vehicles.
2. Actual costs method based on running costs, apportioned for business use.

If you use simplified mileage rates for a vehicle, you should keep that method consistently for that vehicle while you continue using it for the business.

30-Minute Mileage Checklist Before Filing

Use this workflow to reconcile your completed 2025/26 log before filing.

1. Backfill missing trips from your real calendar

Review your diary, job sheets, invoices and messages covering 6 April 2025 to 5 April 2026. Reconcile gaps against reliable evidence; do not invent journeys or mileage.

For each journey capture:

• date
• start and end locations
• business purpose
• miles

2. Remove non-allowable journeys

Delete or reclassify trips that are private or not allowable business travel. This one clean-up step reduces the risk of over-claiming.

3. Standardise trip notes

Inconsistent trip notes are a common weak point during record checks. Normalise wording now, for example:

• “Client meeting - Manchester site”
• “Supplier collection - parts order”
• “Bank visit - business deposit”

Short, specific, repeatable notes are better than vague notes like “work errand”.

4. Confirm your method before you total the year

Do not mix methods casually at year-end. If this vehicle is on simplified mileage, keep it there unless you have a clear, compliant reason to change on a valid boundary.

5. Run a duplicate and outlier pass

Sort by date and distance. Look for:

• accidental duplicates
• obvious distance spikes
• wrong date year entries
• impossible same-time overlaps

6. Export your year-end summary

Produce a clean annual total plus monthly breakdown. Save it with a clear file name, for example:

mileage-summary-2025-26-exported-2026-10-02.csv

7. Save supporting evidence in one folder

Store mileage summary plus supporting docs (calendar entries, invoice references, appointment logs) in one place so you can respond quickly if HMRC asks questions.

Common Mistakes Before Filing

1. Mixing 2026/27 trips or its 55p rate into the 2025/26 return.
2. Including private travel because trip purpose was not tagged.
3. Mixing mileage method and actual-cost method without clear treatment.
4. Relying on memory instead of contemporaneous logs.
5. Filing numbers without a retained evidence pack.

Employee vs Sole Trader: Where P87 Fits

This post is aimed at Self Assessment filers who are claiming business expenses as part of their return.

P87 is primarily an employee tax relief route for eligible job expenses. If you already complete a Self Assessment return, claims are normally handled through that return rather than as a separate P87 process.

This distinction matters because users often mix these routes when searching for mileage allowance help.

Record Retention Rule You Should Not Ignore

For self-employed records, plan to keep supporting records for at least 5 years after the 31 January submission deadline for the relevant tax year.

For the 2025/26 year filed by 31 January 2027, this generally means retaining records into 2032. Keep a clear digital folder structure now so you are not reconstructing records years later.

Official HMRC/GOV.UK References

• Expenses if you’re self-employed: travel
• Simplified expenses: vehicles
• Rates and thresholds for employers 2026 to 2027
• Self Assessment tax return deadlines
• Business records if you’re self-employed: how long to keep your records
• Claim tax relief for your job expenses (overview)

Turn This Into a Repeatable Monthly Routine

Do one 15-minute mileage review each month, then a final year-end sweep in late March. This keeps April cleanup small and January filing less stressful.

Track mileage on iPhone with DriveLog.

If you are also comparing simplified rates and claim methods, this companion page can help: HMRC mileage rate 2026/27 update.

FAQ: Claiming Mileage on Self Assessment

Can I claim mileage on Self Assessment as a sole trader?

Usually yes, for allowable business travel. Keep accurate records and make sure private travel is excluded.

What is the tax year-end date I should use for 2025/26?

The 2025/26 UK tax year ended on 5 April 2026.

When is the filing deadline for the 2025/26 return?

The standard online deadline is 31 January 2027, with payment due by the same date.

Do I use P87 or Self Assessment for mileage claims?

If you file Self Assessment, claims are generally made through your tax return. P87 is generally used by eligible employees claiming job expense relief outside Self Assessment.

How long should I keep mileage records?

For self-employed records, keep them for at least 5 years after the 31 January submission deadline for that tax year.

What if some trips are missing from my log?

Reconstruct them as soon as possible using calendar, invoices, and other business evidence. Mark estimates clearly where needed and avoid guessing without support.