According to the interpretation of the State Administrative Agency, if your business only offers mail addresses, then it does not need to register as a provider of corporate services. An administrative address is the address that is entered in the Trade Register, for example. A mailing address is the address where a company wants its post delivered. If your client wants an administrative address and your business offers it, your business must register as a provider of a business service. When your clients use the address of your company as their address in the Trade Register, your business will be seen to offer corporate services.
The reason why this is done has no bearing on the matter; for example, it may simply be that the client of your business is a micro-enterprise that has no premises of its own, and it operates from the home of the entrepreneur, for example, an apartment, and that the address of your company is entered in the Trade Register as the client's address for reasons of credibility. If your business offers a different postal address for reasons other than mere “practicality”, this means that a business service is being offered.