Quiere decir que pertenece o no pertenece a la corporación, a la compañía.

Depende de la normatividad de cada pais por lo general las primeras son sociedades y las segundas son solo un individuo o persona fisica

A Massachusetts business trust or MBT is a legal trust set up for the purposes of business in the state of Massachusetts. They may also be referred to as an UNINCORPORATED BUSINESS ORGANIZATIONS or UBO

An unincorporated entity in Australian law is an entity that has the same characteristics as a company but is NOT incorporated as a corporations law company.

This includes:

a branch of an overseas company not incorporated in Australia (often the name ends in corporation)
incorporated associations which are incorporated under an Act of one of the States and territories of Australia, and
incorporated charitable institutions.
people grouped together by a common purpose with club-like characteristics, for example, a sporting club, social club or trade union.

In México that would be "Sociedades Irregulares". That is, companies which haven't fulfilled all legal requirements to be recognized as legally valid.

In the US the document which some states issue to prove a corporation's existence upon the filing of articles of incorporation is the Certificate of incorporation. In most states the articles are sufficient proof.

On the other hand, a De facto Corporation is a company which operates as if it were a corporation, accepted for practical purposes, although it has not completed the legal steps to become incorporated (has not filed its articles, for example) or has been dissolved or suspended but continues to function. The court temporarily treats the corporation as if it were legal in order to avoid unfairness to people who thought the corporation was legal.

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