Under what condition does trademark "incontestability" occur?

Trademark "incontestability" is a legal status that strengthens the validity of a trademark after certain conditions are met. The correct condition for a trademark to achieve incontestability is after five years of continuous use in commerce, along with the owner properly filing a declaration of incontestability with the United States Patent and Trademark Office (USPTO).

This five-year period allows the trademark owner to establish that the mark has become a stable part of the market, thereby gaining a heightened level of protection against challenges. Importantly, the filing—the specific legal paperwork that must be submitted to the USPTO—is essential to achieve incontestability, as it formally declares that the trademark has been used consistently for the requisite time frame and satisfies the criteria set forth in pertinent statutes.

The other conditions listed do not satisfy the requirements for incontestability. For example, three years or any duration of use without the necessary filing does not lead to this status, nor does seven years of continuous use without filing meet the stipulated necessity for legal declaration. Thus, the specific combination of five years of use and proper filing is what confers the trademark the status of being incontestable, bolstering the owner's rights against potential claims of invalidity.