What is professional use and how do you determine it for your expenses?

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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.

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

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.

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)

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.

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 ?