When a natural person is entered into the commercial register the company provides also the signing rights. Common signing rights include “with sole signature” or “with collective signature of two”. While the former provides the person full discretion to sign alone, the latter requires that the person needs at least one additional signature. This basically reflects the four-eyes principle. Importantly, the signature must be provided by a person also entered in the commercial register. Further variations exists, but are rather uncommon. Usually the commercial registers provide very detailed information on their websites. For example, the canton of Zurich: https://www.zh.ch/content/dam/zhweb/bilder-dokumente/themen/wirtschaft-arbeit/handelsregister/häufige-fragen/fragen_und_antworten.pdf