Field help:
Rental income for flats rented out to relatives
Renting out to relatives is subject to special examination by the tax office.
If the rental income is at least 66% of the usual local rent (including allocations), the transfer is fully paid and the income-related expenses are generally recognized in full by the tax office.
If, on the other hand, the actual rent is less than 66% of the usual local rent, this is a subsidised or partially subsidised transfer. In this case, the income-related expenses are only recognised by the tax office on a proportional basis, meaning in the proportion between the actual rent and the usual local rent.