If it is a Grantor trust, the income will pass out on a grantor tax letter (if a 1041 is done, and the grantor trust has its own EIN).  This happens most of the time when the grantor becomes incapacitated and a successor trustee takes over.  Typically it is reported under the grantors SSN.  If its a simple irrevocable trust, the income will still pass pass out (even if they don't get a distribution).  A complex trust (complex $100), you can keep the income in the the trust and pay it at the trust level.  You can just leave the DNI in the trust (no distributions, no income will pass out).  A complex $300 income is typically required to be passed out.  Not sure if that helps you or not.