How do you calculate your mileage allowance in 2026?

Working out your mileage allowance means turning business trips into a deductible amount, based on a scale published each year by the tax authorities. The principle looks simple, yet three variables are enough to complicate matters as soon as you do it by hand: the vehicle's fiscal power, the total distance driven over the year, and the nature of each trip. On top of that sits a little-known twist — every kilometre of the year is recalculated once you cross a threshold — which trips up most end-of-year calculations. This article explains how the scale that applies in 2026 works, how to get an accurate figure trip by trip, and which records make your allowance defensible if the tax office ever asks.

How does the mileage rate work in 2026?

The mileage rate is a flat per-kilometre allowance that covers the full running cost of a personal vehicle used for work: fuel, of course, but also servicing, tyres, insurance and — above all — depreciation, the item almost everyone underestimates. This flat rate is set by an order published each year, usually in spring, and then republished on the official tax website. Its structure is stable from one year to the next: the rate depends on the vehicle's fiscal power and on the total distance driven during the year. Until the new year's order is published, the most recent scale serves as a provisional reference — worth keeping in mind for the first months of the year, ready to adjust later.

The vehicle's fiscal power

The fiscal power, expressed in tax horsepower and shown on the registration document, sets which column of the scale applies to your vehicle. Brackets run from 3 hp and below up to 7 hp and above for cars. The higher the power, the higher the per-kilometre rate, on the logic that running and depreciation costs rise with engine size. In practice, the same round trip does not yield the same allowance in a 4 hp car as in a 7 hp one. That is why it pays to enter this figure once, correctly, rather than fixing it afterwards across dozens of trips already logged.

The three distance brackets

The scale sets out three annual brackets that reflect how costs taper. The first, up to 5,000 km, applies a plain per-kilometre rate. The second, from 5,001 to 20,000 km, blends a reduced rate with a fixed component — a distance multiplied by a coefficient, plus a set amount in euros. The third, above 20,000 km, returns to a per-kilometre rate designed for heavy drivers. This tiering captures a common-sense idea: the more you drive, the less each extra kilometre weighs proportionally, because fixed costs spread over a larger distance. The table below shows indicative first-bracket rates by fiscal power.

These figures come from the latest published scale (2025) and serve as a benchmark; confirm the year's coefficients once the 2026 order appears.

The electric vehicle case

For an electric vehicle, the amount produced by the standard scale is increased by 20%. This top-up recognises the specific running conditions of these vehicles and applies to the final result, whatever the bracket. It is automatic as soon as the vehicle is electric, with no trip-by-trip justification required. It is a detail regularly missed in manual calculations, even though it noticeably changes the yearly total. Across a run of weekly appointments, the 20% gap between a calculation that applies the top-up and one that ignores it is far from trivial, and feeds straight into the deductible amount.

How do you calculate the amount of your mileage allowance?

The calculation always follows the same steps: work out the distance to be counted, identify the right bracket based on the running annual total, apply the matching rate, then add the electric top-up where relevant. Trivial for one trip; a source of errors and wasted time once repeated across dozens of journeys. A mileage expense app applies the scale automatically, updates the annual total with every new trip, and handles the bracket switch on its own. You enter a start point, a destination and a distance; the tool returns a compliant amount and files it in the right year, removing the bracket errors and missed top-ups that inevitably creep into a spreadsheet.

The distance counted (round trip)

The distance counted is the kilometres actually driven for a business reason, out and back when the trip involves a return to the starting point. A meeting 18 km away therefore counts as 36 km if you drive home afterwards — an obvious point that explains half the gaps found in rough logs. Distance is best measured on a realistic road route: a routing calculation, based on a mapping service such as OpenStreetMap, gives a far firmer basis than an estimate from memory, and stands up better to scrutiny. Always taking the road distance, rather than the straight-line one, avoids both underselling yourself and unwittingly inflating the total.

A worked example

Take a concrete example: a 5 hp vehicle, a meeting 18.2 km away, driven as a round trip, so 36.4 km counted. In the first bracket, at a rate of around €0.636 per kilometre, the allowance for that single trip comes to about €23.15. The figure looks modest, but set against a week of sales calls, then a month, then a full year, it builds into amounts that genuinely count in an actual-costs claim. That accumulation is exactly why regular entry beats reconstruction: rebuilding twelve months of trips at year-end always yields an approximate result — usually understated — and eats hours no one wants to spend.

The retroactive annual recalculation

Here is the technical point almost everyone misses: when you cross a bracket, the formula applies to the total annual distance, not only to the kilometres above the threshold. Passing 5,000 km during the year therefore changes the calculation of every kilometre of that year, with a retroactive effect on what has already been entered. Redoing this by hand is one of the first causes of spreadsheet errors, because you have to remember to reprocess the whole history at the right moment. A tool that recalculates the running total on every entry keeps the figure correct at all times, without you having to watch the thresholds yourself.

What records do you need for mileage expenses?

The scale spares you from keeping fuel or servicing invoices, but not from proving the reality of the trips that underpin the allowance. In practice, each journey must tie back to an identifiable business reason: a client, a site, a training course, a trade show. Calendar sync is a real help here, since it links a trip to a dated, located appointment, forming a coherent and hard-to-dispute trail of evidence. The closer the record is to the trip itself, the more convincing it is; a log rebuilt months later, with no anchor in a calendar, always leaves room for doubt.

The trip log

Keeping a trip log — date, reason, start and end points, distance — is the backbone of a solid file. It need not be elaborate, but it must be regular and consistent with the reality of your activity. Entering trips as you go, right after each one, produces a reliable, continuous history; a late reconstruction inevitably leaves gaps the tax office can flag. The point of a mobile tool is precisely to make that entry fast enough to become a reflex, rather than a chore put off until later and finally rushed.

Consistency with the calendar

Documentary consistency matters as much as the accuracy of the figure. A trip backed by an appointment in your calendar, with an identifiable place and time, holds up far better than an isolated line in a spreadsheet. Automatically matching your appointments with your expenses reduces the risk of inconsistency between what your calendar says and what your claims declare, and saves considerable time for people running from visit to visit. That consistency is also what makes an audit calm: the pieces line up, the story holds, and there is nothing to rebuild under pressure.

Keeping the evidence

Finally, keep your records for the legal retention period that applies to your situation, counted in years. Dated, backed-up, exportable digital storage beats a paper notebook that goes missing or a shoebox of faded receipts. The aim is twofold: to find information in seconds when you need it, and to present an orderly file if the question arises, without rebuilding everything under pressure. A tool that centralises trips, receipts and running totals, and exports them on demand, turns that retention duty into a mere formality.

Mileage rate and tax: the points to watch

Beyond the calculation itself, a few tax rules frame how the scale is used and determine whether your allowance is genuinely deductible. Knowing them avoids building a file that is technically right but fiscally fragile.

Actual costs or standard deduction

The scale falls under the actual-costs option: by choosing it, you give up the standard allowance in order to deduct all your justified business expenses, trips included. This option is only worthwhile if your total actual costs exceed the standard allowance you would otherwise have received, which is checked each year against your situation and mileage. Running the comparison before deciding avoids sticking with a less favourable route out of habit; heavy drivers often find actual costs clearly advantageous, but the check remains essential case by case.

Caps and mixed use

The scale includes power caps: above a certain fiscal horsepower, the top column applies and you go no further. It also assumes genuinely business use of the vehicle. For a vehicle in mixed use, private and business, only the business kilometres enter the calculation; personal trips are excluded. The line between uses must stay clear, consistent and documented, or the whole deduction becomes fragile if questioned.

Yearly update of the scale

Finally, the scale is revised every year by order: the 2025 coefficients are not necessarily those of 2026, even if the structure rarely changes. You therefore need to watch for the order's publication and update your settings at the right time, rather than applying last year's figures out of inertia. A tool that builds in the scale and keeps it current spares you that regulatory watch, while preserving a record of the versions used for each year — so your calculation stays consistent from one period to the next.

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