When to file K-1s
The trust needs to file a return if it has a gross income of $600 or more during the trust tax year or there is a nonresident alien beneficiary or if there is any taxable income. An estate needs to file a return if it has a gross income of $600 or there is a nonresident alien beneficiary. The 1041 reports income retained by the trust or estate, as well as the income distributed to beneficiaries, but income taxes are only paid by the trust or estate if the distributions are required. Unless the trust document specifies otherwise, capital gains and losses stay with the trust since they are part of the corpus.
For example, suppose you’re a trustee, and the terms of the trust require all dividend income from a stock portfolio must be distributed equally among the beneficiaries. You must report all dividend income on the 1041, and you report the share of dividend income for each beneficiary on Schedule K-1s. You must furnish a copy of each K-1 to the appropriate beneficiary, and attach all copies to Form 1041 when you file the return with the Internal Revenue Service.