Loans for Mixed-Use Buildings: These Mistakes Cost You Real Money
You live on the ground floor and rent out the upper floor. Or: you've bought a house that you use partly as an office and partly as a home. In these situations, one of the most common and costly tax traps for property owners lurks: the incorrect allocation of loan interest.
Basic rule: loan interest is fully deductible – but only for the rented portion
Interest on a loan taken out to finance a rented property is fully deductible as income-related expenses. This is one of the greatest tax advantages in property financing. For owner-occupied portions, however, this does not apply – these interest payments are private and non-deductible.
The central problem: which money goes to which part?
With mixed-use buildings, the question of which loan finances which part of the property determines how much of the interest you can deduct. And this is where many people make a critical mistake: they mix everything in one account.
⚠️ The most common mistake: a single construction account for everything
If you mix €400,000 of borrowed capital and €100,000 of equity in a single account and use it to build a house that is half owner-occupied and half rented, you can automatically only deduct 50% of the interest – based on the floor area allocation. This doesn't have to be the case.
💡 The solution: separate construction accounts from the outset
Set up two separate accounts from the start: one for the rented portion (loan funds only), one for the owner-occupied portion (loan funds + equity). This ensures the entire loan is allocated to the rented portion – and thus all interest is deductible.
📊 Calculation example: what the right account structure achieves
Two-family house, €250,000 per half. Loan: €400,000, equity: €100,000. Wrong: everything in one account → 50% of interest deductible. Right: Construction account 1 (rental): €250,000 loan. Construction account 2 (owner-occupied): €150,000 loan + €100,000 equity. → 62.5% of interest deductible. At 3% interest on €400,000 = €12,000 interest/year. Difference: €1,500 more deductible expenses per year. At 42% tax rate: €630 tax saving per year – over 20 years: €12,600.
Special rules for married couples
There are also important rules to observe for married couples. As a general rule: if both spouses took out the loan jointly, the owner spouse can deduct all the interest – regardless of who actually pays. It's different if only one spouse takes out the loan but the other owns the property: in that case, the interest is not deductible.
What counts as deductible financing costs?
These costs you can deduct:
- Ongoing loan interest
- Commitment interest
- Discount/disagio (immediately deductible under certain conditions)
- Early repayment penalties (when redeemed during the rental period)
- Notary and court fees for land charge registration (but not for the purchase contract itself)
⚠️ Repayment is not deductible!
A common misconception: only the interest counts as income-related expenses – not the repayment. You must pay the repayment from taxed income. However, the tax refund from the interest deduction can help finance the repayment.
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