irrevocable trust means nothing. a critical question is - is the grantor (the person who put the assets in the account) the same as the beneficiary or the beneficiary's spouse. this or certain other abilities of the grantor would make this a grantor trust. the grantor would pick up the income. if it is because there is an EIN number a grantor trust return must be filed.
if it is not a grantor trust than a regular trust return must be filed. whether the trust pays the taxes on the income or the income is distributed to the beneficiaries would depend on the wording of the trust.
