if the trust obtained an EIN and the assets were registered using that EIN rather than the individual's SSN, a trust return was due. many grantor trusts do not obtain an EIN so they use the grantor's SSN.
since a grantor trust does not pay taxes there's little the IRS can do except impose a penalty of $100 per year. however, your would be filing late so the penalty could apply. if the IRS issues a penalty notice you could always ask for abatement since the income was properly reported on the grantor's return.
