You use several flats in Germany. Perhaps one of them belongs to you while the other is rented. For registration law (Meldewesen) classification this contractual difference is not sufficient. Main and secondary residence are determined according to the statutory framework and the actual living circumstances, not solely by a chosen designation.
Usage is a statutory starting point
§ 21 BMG designates one of several residences in the country as the main residence. As a principle it names the predominantly used residence; every further residence in the country is a secondary residence. The provision also contains notification duties regarding the main residence and changes. [MEHRERE]
This principle is supplemented by § 22. For certain married people or those living in a civil partnership the predominantly used family or partner residence is decisive there. There are separate provisions for minors. In cases of doubt the norm deals with the focus of life relationships. [HAUPT]
It would therefore be imprecise to resolve the entire individual case solely with the statement “I am there more often” or with a blanket day calculator. The actual constellation must fit the relevant rule.
Create a clear factual overview
Describe which flats you actually use and how your ordinary daily life is distributed between them. Note essential family connections and changes, insofar as they are relevant for the concrete classification. Separate existing use from merely planned wishes.
The overview is an editorial preparation aid for the discussion with the registration authority. It does not require a public collection of private life details. Submit only the information needed for the specific procedure via the appropriate official channel.
An example with two different questions
In the fictitious case one flat is used at the place of work, while family living relationships exist at another place. The person concerned wants to know which flat is to be treated as the main residence for registration purposes. They present the authority with the actual constellation instead of automatically declaring the owner-occupied flat to be the main residence.
In addition they raise a tax question regarding the work-related housing situation. This is passed on separately. The registration classification is not to be taken unexamined as a complete answer on tax residency, a municipal charge or the recognition of certain costs. The article does not decide these consequences.
Take changes into account consciously
If your daily life changes, the previous classification should also be reconsidered. A status chosen correctly in the past is not an answer to an actual situation that has since changed. § 21 contains its own notification requirements precisely for changes. [MEHRERE]
If in doubt ask about the appropriate procedure and the evidence required. Do not submit contradictory registrations as an experiment to achieve a desired result. A factual declaration of actual use is the better basis.
What to keep after clarification
Secure the official confirmation and the explanation relevant to you. Record other outstanding legal questions separately. This overview does not replace an individual status decision, especially not in complex family, protection or cross-border situations.
Its usefulness lies in preparation: you know the statutory reference points, can describe your actual daily life clearly and avoid equating contract, ownership, preferred address and registration main residence.