unreported; not officially registered; failing to report
Used for something that should have been reported or registered to an authority but has not been. Often appears in legal, administrative, or formal contexts, such as unregistered marriages, unreported income, or unlicensed businesses.
An unregistered marriage is not legally recognized.
Unreported business operations are subject to penalties.
Formed from the negative prefix 未 “not yet; un-” and 届け “report; notification.”