Do you use your car for both business and private purposes? Then you'll need to determine what share of your mileage is professional. This percentage determines:
how much VAT you can reclaim on your car expenses
how much you can deduct on your personal income tax
The higher your professional use, the more you can deduct. But the tax authorities will also expect you to be able to substantiate this percentage in case of an audit.
The formula is simple: you divide your business mileage by your total mileage.
(number of professional km per year ÷ total number of km per year) × 100
Example: in 2025, you drive a total of 20,000 km, of which 13,000 km are for professional purposes.
→ Your professional use: (13,000 ÷ 20,000) × 100 = 65%.
There's an important exception to keep in mind: your daily commute.
Your commute to a fixed workplace counts as private use, not professional use. Even though it's a trip you make for work, tax law treats it as private travel, for both VAT and personal income tax purposes.
📆 The 40-day rule: a location only counts as a "fixed workplace" (and therefore as commuting) if you are present there for 40 days or more during the year, not necessarily consecutively. If you work somewhere fewer than 40 days per year, for example at a client's site, in a co-working space, or on a temporary construction site, then that trip remains professional travel.
The VAT authorities allow you to choose between three methods for determining your professional use. You should choose the method that best suits your situation.
Method | How does it work? |
1. Mileage register/log | You record every journey: the date, the departure and arrival addresses, the distance in kilometers, and the purpose of the journey. This is the most accurate, but also the most time-consuming, system. |
2. Home-work formula | A fixed formula based on your home-work distance: (home-work distance × 2 × 200 working days + 6,000 other private km) ÷ total km × 100 = % private use. Your home-work commute counts here as private - not as professional. Your professional use is 100% minus that private percentage. This only applies to 1 car per user, and you always use 200 days in the formula, even if you often work from home. |
3. Fixed 35% flat rate | The simplest option: you fix your professional use at 35%, without needing a mileage register. Note: you then need to stick to this for at least 4 consecutive calendar years, and apply it to all your mixed-use vehicles. |
Not always, it depends on your professional use percentage.
Up to around 35%, a reasonable estimate is usually enough, for example based on your calendar or client visits.
From around 35% onwards, the tax authorities generally expect a mileage register or other detailed proof. The higher your percentage, the stronger the burden of proof needs to be.
You can keep a mileage log in a simple Excel or Google Sheets table. Make sure it meets the legal requirements.
In the log, you simply enter:
date of the trip
starting and ending odometer readings
departure and arrival address
purpose of the trip (business or private)
Based on this data, you can add up your total number of kilometers yourself and calculate your professional-use percentage.
Your professional use percentage isn't the only percentage that matters for your car. There's also VAT deductibility, which is a separate, legally fixed rule specifically for vehicles.
35%: the legal flat rate. This is the default, and you don't need any proof to apply it.
50%: the legal maximum. You can only apply this if you can prove a higher business use, for example with a mileage register.
100%: only for professional drivers (taxi, delivery, rideshare, etc.), where the vehicle is used exclusively for the activity.
For each expense, you can indicate the professional percentage. For example, if you drive 35% professionally, enter this for every car expense. Accountable then automatically takes this into account for:
the VAT deduction;
and the calculation of your personal income tax.
VAT deductibility works differently: you set it once per car, not per expense. When you add a passenger car under your car settings, indicate which VAT deductibility applies (35%, 50%, or 100%, see the section above). Accountable then applies this automatically to every expense linked to that car.
🚨 This VAT deductibility setting only applies to passenger cars. Utility vehicles follow different rules and are usually 100% deductible after professional use. You add the professional use directly to the expense, utility vehicles don't require you to add a car in the settings.
You simply need to encode the expense under the Utility vehicle category, then select the relevant subcategory. You don’t need to link a vehicle to the expense, since it is a utility vehicle and no CO₂ formula applies.
💡 Want to know more about how professional use works for your other expenses (phone, home office, laptop...)? Check out this article.
Not sure which method or percentage best fits your situation? Your tax coach is happy to think it through with you.
Any questions? We're always here for you in the chat 😊
Author - Valesca Wilms
As content marketing lead at Accountable Belgium, Valesca writes about freelancing, self-employment, and taxes based on her own experience as a freelancer.
Who is Valesca ?Thank you for your feedback!
Useful
As a self-employed individual with a sole proprietorship, your income is taxed under the personal in...
Read moreStarting from 2026, all self-employed individuals will need to send their invoices electronically in...
Read moreThe VAT reverse charge is a complicated word for a simple concept. It helps you purchase and sell sm...
Read moreThey always answer right away to any question I have, they provide clear answers, and they are very patient even when I struggle to understand. They try to explain in different ways. They are very helpful, responsive and friendly.
Chiara Marradi
01/05/2026
Everything was great! All my questions were answered quickly and in a friendly manner.
Wenzeslawa Wegener
04/05/2026
In the world where everyone seems to be out to get small entrepreneurs and overwhelm them with new rules, more taxes and reporting obligations, Accountable often feels like the one steady partner that actually wants you to succeed, providing quick, clear and personalised support. Thank you!
Janina Arsenjeva
10/04/2026
This is an amazing application with great support on issues. In short as in day I am addicted to it (in a positive way). I myself is from IT project management and the way they have captured the user requirement, it’s phenomenal.
Sumit Tewary
01/12/2024
UI is great. Feature packed and very easy to use. The team at Accountable were VERY quick to respond and their team of technicians soon had a fix in place. Very happy with the level of service so far. Thumbs up from me!
Dean Osborne
14/06/2023
This program is a lifesaver, and it is always improving. Plus, it has an AI chat feature that is actually useful.
Jeffrey Humble
14/01/2026
The coaching session on tax management was excellent, good material, excellent explanations and very insightful. Combined with the AI I never feel alone with Accountable.
Sergio Barbarino
23/04/2026
The availability of your team to help and guide people to understand their finances better is what really makes Accountable valuable. While the AI is able to give answers to most basic questions, specific scenarios need counsel from a human which your team performs beautifully.
Sofiya Bogdan Neves
18/04/2026
Fast and careful answers from Alina. Top service. Thank you.
Anonymous
15/04/2023
They always answer for questions wherever is via direct e-mail or through app. If they can’t answer fully they will forward you to the right place. Documents were always prepared well and ready to send further to government. Everything is intuitive in the app and easy to sort out even for someone completely green in this field.
Anonymous
22/03/2026
