Complex sentence: Owners of these foreign-held assets must report them on US tax returns if they are worth more than $50,000 and those who do not would be subject to a 30-percent penalty on the balance of the account in question.
Split into simpler sentences: Owners of these foreign-held assets have to report them on tax returns if they are worth more than $50,000. Individuals who do not disclose these assets may be subject to a 30-percent penalty on the balance of the account in question.