What is professional use?
As a self-employed person in Belgium, you can deduct expenses related to your business activity. However, many expenses are not used exclusively for work. Your phone, car, internet connection or even part of your home may also be used privately. Professional use (sometimes called business use or professional percentage) is the percentage of an expense that relates to your self-employed activity.
This percentage is used to calculate:
your deductible expenses for personal income tax (IPP);
and the VAT you can reclaim.
Why does it matter?
Professional use directly impacts two things:
• Your income tax
The higher your professional use, the more expenses you can deduct — which reduces your taxable income.
• Your VAT recovery
VAT can only be reclaimed up to the professional-use percentage, and within certain legal limits (for example: a maximum of 75% for phone expenses).
The tax authorities expect this percentage to be:
realistic;
consistent with your activity;
and justifiable in case of an audit.
🚨 Important: overstated professional use is one of the most common audit triggers.
A reasonable, well-documented percentage is always safer than an aggressive one you cannot justify.
How do you determine the right percentage?
There’s no universal percentage. It depends on the type of expense and how you actually use it.
Here are the most common allocation methods used in Belgium:
• Time-based allocation
For subscriptions such as phone plans, internet or software, estimate how much time is spent on professional use versus total use.
• Surface area
For home-office expenses, calculate the share of your home used for work (office, studio, workshop…) compared to the total living space.
• Kilometres driven
For cars, compare business kilometres (excluding commuting) with the total kilometres driven over the year.
• Estimated use
For mixed-use items such as laptops, cameras or furniture, apply a realistic percentage that reflects your actual professional use.
Concrete examples
1. Phone and internet subscription
You use your smartphone mainly for work-related calls, emails and admin tasks.
A reasonable professional-use percentage could be around 70%.
👉 Example: your monthly subscription costs €50 incl. VAT.
Professional use entered in Accountable: 70%
VAT limit for phone expenses: 75%
Recoverable VAT: 70% of the VAT paid
Deductible expense for IPP: 70% of the amount excl. VAT
💡 If your subscription also includes TV services, that part is not considered professional and should be excluded from the calculation.
2. Personal car used for business
You drive 20,000 km per year in total, including 6,000 km for client meetings.
Your professional use is therefore 30%.
👉 Example: you purchase a car for €30,000 incl. VAT.
Professional use: 30%
CO₂ deductibility rate: for example 60%
Depreciation: 20% per year over 5 years
Calculation:
€30,000 × 30% × 60% × 20%
= €1,080 deductible per year
The same logic applies to:
fuel;
insurance;
maintenance;
and repairs.
💡 Keep supporting evidence for your business trips, such as a calendar, mileage log or spreadsheet listing business kilometres.
3. Home office
You work from a dedicated 12 m² office in a 100 m² home.
Your professional-use percentage for home-related costs is therefore 12%.
👉 Example: your annual electricity bill is €1,500 incl. VAT.
Professional use: 12%
Deductible expense: €180
Recoverable VAT: same percentage (if the invoice is issued in your business name)
💡 In practice, the tax authorities generally tolerate up to 15% professional use of a home without requiring additional justification. Above that threshold, make sure you can support it with floor plans, measurements or photos.
4. Laptop
You buy a laptop for €1,800 excl. VAT and use it:
80% for your business;
20% privately.
Professional use: 80%
Depreciation period: 3 years
Annual deduction: €480 per year
Recoverable VAT: 80% of the VAT paid
5. Meals, clothing and mixed costs
Some expenses remain limited or non-deductible even when they are linked to your business activity.
Non-deductible
everyday clothing;
lunches eaten alone.
Deductible under conditions
profession-specific clothing (medical scrubs, safety equipment, lawyer’s robe…);
restaurant meals with clients: deductible up to 69%.
Common mistakes to avoid
• Setting everything to 100%
This is one of the biggest audit red flags. Be realistic.
• Not keeping supporting documents
A mileage log, calendar, floor plan or usage estimate can make a big difference during an audit.
• Confusing professional use with deductibility
Professional use reflects your actual usage.
Deductibility refers to the legal limits imposed by tax law.
The two work together.
Where do you enter professional use in Accountable?
When creating an expense, simply complete the “Professional use” field located below the expense category.
Just enter your estimated percentage — Accountable automatically applies:
VAT limitations;
deductibility rules;
and the relevant tax calculations for your situation.
💡 Not sure which percentage to use?
Our tax coaches are here to help.
Have a question about a specific expense?
Reach out via the in-app chat or email us at support@accountable.eu.