Company car logbook in Luxembourg: template, rules and proof of private kilometres

In Luxembourg, the company car logbook ("carnet de bord") is the alternative to the flat-rate method for valuing the benefit in kind of a company car: private kilometres, including the commute between home and work, are multiplied by the car's cost per kilometre. It is only mandatory when employer and employee choose this method instead of the flat rate of 0.5 %, 0.6 % or 2 % of the catalogue price.

This guide is for HR, payroll and fleet managers, and for drivers themselves. It explains what the Grand-Ducal Regulation requires, which columns a usable logbook needs, how the cost per kilometre is calculated, when the logbook pays off and why it almost never does for cross-border workers. At Voltaback we read the odometer directly from the connected car, with no box and no location data sent to the employer.

The essentials in 30 seconds

• Legal basis: article 3 a) of the amended Grand-Ducal Regulation of 23 December 2016 implementing article 104 of the income tax law (L.I.R.).
• Mandatory? Only if you choose the logbook method. Under the flat rate, tax law requires no logbook.
• Calculation: private kilometres for the month × cost per kilometre (set by the employer), valued monthly, logbook attached to the payroll record.
• Pays off for: an expensive car at the 2 % rate with few private kilometres.
• Rarely pays off for: an EV at 0.5 %, and almost never for cross-border workers, whose commute counts as private.

What is a company car logbook?

A logbook is a continuous record of the trips made with a given car: date, odometer at start and end, destination, purpose, and whether the trip is business or private. In Luxembourg the French term "carnet de bord" is used in official texts; in German, "Fahrtenbuch".

Two related terms should be kept apart:

• Mileage log or odometer list: only the odometer reading on fixed dates, for instance at month end. It is enough for leases, maintenance and reporting, but it does not prove private kilometres.
• Logbook in the tax sense: it separates business and private kilometres and is the basis for valuing the benefit in kind at cost per kilometre.

Search for "company car logbook" in English and you mostly find UK guides built around HMRC rules, or software sold for those rules. Neither applies in Luxembourg: format, rates and case law are different. This guide relies only on Luxembourg texts.

What does Luxembourg law say about the logbook?

Article 3 of the amended Grand-Ducal Regulation (RGD) of 23 December 2016 sets two valuation methods for a car provided by the employer.

a) Valuation at cost per kilometre ("prix de revient kilométrique"). The employee keeps a logbook recording all private trips, including the journey between home and work. The logbook is attached to the payroll record. The employer establishes the car's cost per kilometre. The benefit equals private kilometres multiplied by the cost per kilometre, valued monthly.

b) Flat-rate valuation. It replaces method a) with a monthly percentage of the new price including options and VAT, minus any discount granted. The same value applies to leased, rented and used cars.

What that means in practice:

• The commute is private. This rule has the biggest impact on the result, especially for long commutes.
• Valuation is monthly. A logbook filled in once a year from memory does not match the wording of the regulation.
• Two ways to derive private kilometres. Guichet.lu describes the practice like this: the employee records business kilometres, and private kilometres are total kilometres minus business kilometres. Both routes give the same result if the odometer readings are right.
• Like the flat-rate benefit, the logbook benefit is salary. It is subject to wage withholding tax and to social security contributions.

A warning when you read up on it: the English Guichet page on company cars dates from 2015 and still shows a flat rate of 1.5 %. The rates that apply today are in the table below.

Sources: Guichet.lu, tax provisions for company cars; amended Grand-Ducal Regulation of 23 December 2016, coordinated text (Chamber of Commerce).

The 2026 flat rates

Two details often get lost:

• Catalogue price means the full new price including options and VAT, minus the discount granted. It is the same for a leased car and for a used car.
• The consumption threshold is the WLTP value on the certificate of conformity, not the car's real consumption.

A draft regulation approved by the Government Council on 24 July 2026 would extend the EV rates to the end of 2030 and set 1 % for plug-in hybrids at or below 50 g CO2/km from 2027. Until it is published in the Mémorial, it remains a draft. The details are in our article on the benefit in kind of electric company cars.

Source: Klima-Agence, benefits in kind for company cars.

Is a logbook mandatory?

No, unless you choose the cost-per-kilometre method. In most Luxembourg companies the benefit in kind is valued at the flat rate: payroll applies the percentage to the catalogue price, and tax law does not require a logbook.

A logbook can still be useful regardless of the benefit in kind:

• Pool or service cars shared by several employees: who drove when, for instance after a speeding notice?
• Lease monitoring: a monthly odometer reading is enough, without individual trips. See our guide to fleet mileage tracking.
• Employee contributions: a fixed flat contribution is deductible from the benefit, as is a contribution to leasing costs (up to 20 % of the employer's cost). A contribution to variable costs such as fuel or maintenance does not reduce the flat-rate benefit (RGD, art. 4).

Example: employee contribution to the lease payment

An electric car with a €48,000 catalogue price at the 0.5 % rate gives a benefit of €240 a month. The lease payment is €700; the employee pays €200 of it, so the employer bears €500.

• Deductible: at most 20 % of the employer's cost, so 20 % × €500 = €100.
• Taxable benefit: €240 − €100 = €140 a month.
• The remaining €100 of contribution does not reduce the benefit. It is treated as the employee's personal choice, for instance for a better-equipped model.

This follows the pattern Guichet.lu shows for the flat-rate method.

When the car replaces part of the salary

Article 7 of the regulation covers the case where the car is granted in exchange for a reduction of cash salary. The flat-rate logic then does not apply in the usual way: the other costs the employer takes on are subject to withholding tax at their actual value. If your car policy works with salary conversion, have the treatment checked by your fiduciary before choosing between flat rate and logbook.

Service vehicle with no private use

A vehicle that may be used only for business and stays on company premises overnight creates no benefit in kind. As soon as the employee drives it home, there is private use, because the commute counts as private. For tradespeople and technicians who take the van home to drive straight to a client the next morning, clarify the treatment with your fiduciary and write it into the car policy.

Logbook template: the columns you need

The regulation sets no format. What matters is that every private trip is recorded and that the monthly total matches the odometer. You can copy this structure into a spreadsheet or an internal tool.

Three tips for a robust logbook:

• State the business purpose precisely. "Client X, Esch-sur-Alzette" can be checked; "meeting" cannot.
• Reconcile with the odometer every month. The sum of the distances must equal the difference between the odometer at the start and at the end of the month.
• One line per private trip, as the regulation asks, or at least a clear daily summary.

The monthly summary payroll needs

Payroll does not process each line; it needs one figure per month. A simple summary sheet attached to the logbook does the job:

The check is immediate: business plus private must equal total, and total must equal the odometer difference. If one of the two checks fails, the month is not ready for payroll.

Electronic logbook or paper?

The regulation prescribes neither paper nor any particular software. An electronic logbook is therefore acceptable, as long as it contains the same information and can be attached to the payroll record each month. Watch three points:

• Traceable changes: corrections should remain visible rather than overwrite earlier entries.
• Monthly export: payroll needs a PDF or spreadsheet version it can archive.
• Data protection: an app that records every trip by GPS processes more data than the logbook needs. More on this below.

Why odometer readings matter to your fleet

Even if your company applies only the flat rate, you need reliable odometer readings. The benefit in kind is just one of four reasons.

1. Excess kilometres at lease end

Leases set a contract mileage. Excess kilometres are billed at return at a rate per kilometre fixed in the contract. Seeing kilometres monthly lets you swap a high-mileage car with one that drives little, or amend the contract, instead of receiving a large invoice at the end.

2. Maintenance and safety

Services, tyre changes and brakes follow kilometres. Without readings, the fleet misses service dates, with consequences for safety, warranty and residual value. See our guide to fleet maintenance alerts.

3. The benefit at cost per kilometre

For the logbook method, odometer readings are the basis of payroll. A gap between the sum of the entries and the actual odometer is the first thing the tax authority sees in an audit.

4. CO2 reporting and charging costs

Many companies report on fleet emissions, for sustainability reports or client requests. That requires kilometres and consumption per car. For EVs, there is also the reimbursement of electricity charged at home: kilometres and kWh charged must be consistent.

How is the cost per kilometre calculated?

The employer establishes the cost per kilometre of the car provided. The regulation gives no list of costs. In practice, the car's total annual cost is divided by total annual kilometres:

• lease payment, or depreciation and financing costs for a purchased car;
• insurance;
• maintenance, tyres and repairs;
• energy (fuel or electricity);
• road tax (€30 a year for a zero-emission vehicle).

Have your method confirmed by your fiduciary or tax adviser. In an audit by the direct tax administration (ACD, Administration des contributions directes), this is exactly what gets examined.

Example 1: electric car with a €50,000 catalogue price

• Flat rate 0.5 %: 50,000 × 0.5 % = €250 a month, or €3,000 a year.
• Annual costs: lease €7,800, insurance €1,200, maintenance €360, electricity 25,000 km × 18 kWh/100 km × €0.19 ≈ €855. Total ≈ €10,215.
• Cost per kilometre: €10,215 / 25,000 km ≈ €0.41 per km.
• Logbook break-even: €3,000 / €0.41 ≈ 7,300 private kilometres a year.

Someone living 15 km from the office drives about 6,600 km a year on the commute alone (220 days × 30 km). Add weekends and holidays and the threshold is quickly passed. For an electric car, the 0.5 % flat rate is almost always cheaper.

Example 2: plug-in hybrid with an €80,000 catalogue price

• Flat rate 2 %: 80,000 × 2 % = €1,600 a month, or €19,200 a year.
• Annual costs: lease €13,200, insurance €1,800, maintenance €720, energy €3,000. Total ≈ €18,720 for 25,000 km, so €0.75 per km.
• With 8,000 private kilometres: 8,000 × €0.75 = €6,000 a year instead of €19,200 under the flat rate.

Here the logbook cuts the taxable base sharply. It does require strict monthly discipline. All amounts are assumptions: use your own contract data.

At how many private kilometres does it tip?

The table shows the annual benefit for both cars by method, depending on private kilometres per year. The flat rate does not depend on kilometres.

Two conclusions:

• For an EV, the logbook only pays off with very few private kilometres, for a driver who lives almost next to the office and barely uses the car at weekends.
• For a plug-in hybrid or combustion car at 2 %, the logbook stays cheaper well into high mileage. That is where the effort is worth it.

What the difference means for the employee depends on their marginal tax rate and social security contributions: the benefit is taxed and subject to contributions like salary. At a marginal rate of around 40 %, the driver of the plug-in hybrid in example 2 saves several thousand euros of tax a year.

The €0.19 is the price of a kWh charged at night on a Luxembourg dual-rate offer (energy, Creos per-kWh network fee and 8 % VAT). It is not the average price on an electricity bill, which also includes fixed charges.

Decision checklist: logbook or flat rate?

Answer these five questions for each car before choosing. Three "yes" answers or more make the logbook worth calculating in detail; otherwise stay on the flat rate.

1. Is the car taxed at 2 % (combustion, hybrid or plug-in hybrid registered from 2025)?
2. Is the catalogue price high, for instance above €60,000 options included?
3. Does the driver live less than 15 km from the office and work mostly in Luxembourg?
4. Is private use limited, with no long holiday trips and little weekend driving?
5. Will the driver keep the logbook every month, with each business trip documented?

The fifth question is often the deciding one. A logbook abandoned after three months costs more than it saves: the months without a valid record risk being revalued at the flat rate in an audit, and the time spent by payroll on checks is lost. If the driver is not ready for the discipline, the flat rate is the safer choice, even when the numbers favour the logbook.

Cross-border workers: why the logbook rarely pays off

Cross-border workers make up about 49 % of employees in Luxembourg. For them, the rule "commute = private" is decisive.

A cross-border worker living 50 km from work in Germany, Belgium or France drives about 22,000 km a year on the commute (220 days × 100 km). At the cost per kilometre of example 2, that is already €16,500, without a single weekend trip. In example 1 it is over €9,000, three times the flat rate.

In practice: for cross-border workers, the flat rate is almost always cheaper.

A separate question is days worked outside Luxembourg. Beyond 34 days a year (threshold with Germany, Belgium and France; raised from 19 to 34 days for Germany in 2024), the share of salary for those days, benefit in kind included, may become taxable in the country of residence. That is a tax treaty question, not a valuation method question: the logbook changes nothing.

Sources: IGSS, employment dashboard March 2026; KPMG Luxembourg, 34-day rule with Germany.

What about home charging?

No Luxembourg text specifically addresses reimbursing home-charged electricity for a company car. A common reading of the regulation treats energy as a running cost of the car, covered by the flat rate, provided the kWh actually charged are reimbursed at their actual cost. There is no official confirmation of that reading: have it checked by your fiduciary.

For cross-border workers, the real kWh price depends on the country of residence and the individual electricity contract. More on this in our driver's guide to charging a company car at home. Voltaback relies on the home's MID-certified meter, not on a standalone cable meter.

Private car on business trips: mileage allowance, not benefit in kind

A related question concerns employees without a company car who use their own car for business. There is no benefit in kind here, but a reimbursement by the employer.

• Rate: in practice the rate of €0.30 per kilometre applies, the one used for the public sector since 2015 and not indexed. Up to that amount, the reimbursement is treated as free of tax and contributions according to practitioners.
• Proof: the employee submits a statement with date, purpose, route and kilometres. In substance that is a logbook limited to business trips.
• No commute: the journey between home and work is not a business trip and is not reimbursed with a mileage allowance.

The same principle applies to cross-border workers who drive their own car to clients in Luxembourg or abroad. Check details and any caps with your fiduciary.

Source: Pixie.lu, mileage rates in Luxembourg in 2026.

Retention, fines and audits

How long must a logbook be kept?

As an annex to the payroll record, the logbook is a payroll document. Accounting documents must be kept for ten years in Luxembourg under the Commercial Code (article 16). Keep logbooks with payroll records, electronic versions included.

A speed camera photo with a company car

When a company car is caught speeding, the authority first contacts the registered holder, meaning the company or the lessor. To name the driver, the company must know who was using the car at that moment. For personally assigned cars that is simple; for pool cars you need a usage log.

What does the tax authority check?

In a payroll tax audit, the ACD looks at three things: whether the chosen method is documented for each car, whether the cost per kilometre was calculated in a traceable way, and whether the sum of logbook entries matches the odometer readings. A logbook with gaps or round figures risks being rejected. The benefit is then revalued at the flat rate, with back payment of withholding tax and contributions.

Keeping a logbook without manual entry: 5 methods compared

The real obstacle is effort. Someone driving 25,000 km a year fills in several hundred lines.

Voltaback telematics reads the odometer automatically across more than 48 brands, with no box. That gives reliable readings against which the logbook's monthly totals can be reconciled. Classifying each trip as private or business remains the employee's declaration: Voltaback does not replace the logbook required by the regulation and does not produce a document recognised by the ACD.

The driver sees their kilometres in the driver app and no longer has to send a dashboard photo every month.

Data protection: what the employer may know

An odometer reading is not location tracking. To check a logbook, the employer needs the odometer readings and the employee's declarations, not their routes.

If a company tracks the location of its cars, the monitoring regime of article L.261-1 of the Labour Code applies: prior individual and collective information, involvement of the staff delegation, limited retention. The data protection authority, the CNPD, explains these rules.

With Voltaback, the company never receives drivers' location data. Still inform the staff delegation about the other data (kilometres, consumption). More in our article on company vehicle geolocation.

Source: CNPD, vehicle geolocation.

Setting up a logbook in 4 steps

1. Identify the right cars

List cars at the 2 % rate with a high catalogue price whose drivers live in Luxembourg, close to the office. Only there can the logbook be cheaper. EVs at 0.5 % and cross-border workers living far away are usually out.

2. Establish the cost per kilometre

Calculate each car's full annual cost and divide it by the expected total kilometres. Have the method confirmed by your fiduciary before the first payroll month.

3. Write the rule into the car policy

Set the chosen method, the logbook format, the monthly submission date and the odometer check. The driver should know what is expected when the keys are handed over.

4. Automate odometer readings

With automatic readings, payroll has a reliable basis for its check every month. The driver only has to classify private trips.

Reliable kilometres, no extra work for your drivers

The logbook is an effective tool for a few profiles and unnecessary paperwork for most others. The right approach: run the numbers car by car and rely on automatic odometer readings rather than drivers' memory.

To see how Voltaback collects your fleet's odometer readings with no box and no location data sent to the employer, contact the Voltaback team.