A house is partly owner-occupied and partly let. The loan finances payments for both areas. If a calculation treats all interest as tax-deductible, this assumption must be checked before the financing decision. The designation “immobiliendarlehen” does not yet determine the tax allocation.
Name the decisive connection
§ 9 Absatz 1 Satz 3 Nummer 1 EStG lists interest on debt as income-related expenses (Werbungskosten), insofar as they are economically connected with a type of income. § 12 EStG contains, subject to its statutory reservations, the prohibition on deduction for household and living expenses. [ZINS][PRIVAT] The concrete allocation in the case of mixed use therefore requires more than proof that interest has been paid at all.
This page does not prescribe a binding allocation method. In particular, an arbitrarily chosen floor-space ratio is not presented as an automatically sufficient tax benchmark. The legal security of a loan and its actual use of funds must also be distinguished in advice.
A record of use instead of just an annual sum
Assign to the loan the payments actually financed: portions of the purchase price, specific invoices and the respective payment routes. Supplement with the documented use of the relevant areas. For joint invoices, record which allocations are already proven and which remain unclear. Subsequent reminders are not treated like contemporaneous payment receipts.
Tax advice thus has the task of assessing the connection and, where necessary, required allocations on the basis of the actual events. Unauthorised diversion of existing cash flows or retrospective labelling of an invoice is not recommended here as tax planning.
Make the financing error visible
In the hypothetical plan interest of €8.000 falls due each year. The previous calculation applies a purely assumed relief rate of 30 percent to the entire amount: €2.400. As a mere comparison variant only €4.000 interest are assumed to be deductible; the same rate would then yield €1.200. The difference is €1.200 per year or on average €100 per month.
Neither the €4.000 nor the 30 percent are a tax result of the house described. The variant only shows how sensitive the financing can be to an unchecked full deductibility. The total interest payment initially remains the same.
Only supplement the plan after professional classification
Have the actual allocation and the individual tax effect explained separately. Incorporate only verifiably checked approaches, including their time reference, into the further plan. Until then the financing is to be viewed without the unconfirmed relief. This does not pre-empt the tax question; the open assumption merely remains visible.