Am I liable to social security as the sole shareholder and managing director of an Unternehmergesellschaft GmbH?

No. As a rule, you are not: If the shareholder and managing director has a shareholding of 50% or more, this is considered to be a so-called dominant position within the company. There is therefore no “dependency” as with a normal employment contract and the shareholder is treated as a self-employed person.

There is therefore no obligation to pay social insurance (ruling on this: BSG Urt. v. 14. 12. 1999 – B 2 U 48/98 R, GmbHR 2000, 618, 619).