You have to declare the rental income, but if you don't make any profit on the rent, the income is not liable to tax. If, however, you charge a higher rent than you pay yourself or if you provide substantial services (e.g. cleaning, breakfast, etc.) for a fee, you must declare the earnings on your tax return.
Regulations concerning an obligation to register a subtenant vary depending on the locality. In most federal states, you are not obliged to report incoming or outgoing tenants. However, the Federal Registration Act (Bundesmeldegesetz, Artikel § 19 BMG) does require you to participate in the registration process by providing the person required to register with a confirmation of moving in (Wohnungsgeber-Bestätung). You can download the confirmation here as a PDF free of charge (Wohnungsgeber-Bestätigung in german).
Here again, the legal regulations vary from state to state. As a general rule, if your subtenant is there for professional reasons, you are usually not obliged to pay visitors' taxes, city taxes, bed taxes, etc. The tax requirement is also usually waived for lengthier rental terms (generally over approximately one month). By contrast, in the case of a sublease for tourism purposes you should inform yourself of the requirements in your place of residence. This is worthwhile, not least because the amounts are generally easy to settle and not particularly large.
Yes. According to the German Energy Saving Ordinance (EnEv 2014), as the provider of a rental property you must have an energy performance certificate and present it to interested parties at the latest when they view the property. This provision applies to subletting as well. Moreover, you must also include mandatory information concerning the energy performance certificate in ads for the apartment. The energy performance certificate is for the entire building, not just your apartment. If you have not received an energy performance certificate from your landlord, we recommend contacting them to clarify the issue. If no energy performance certificate exists and your landlord is not willing to have one created, you must have one created yourself (e.g. you can order one online).
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