No, the beneficiary does not report nontaxable distributions of corpus or income previously retained and taxed to the estate.
The calculations on Schedule B result in distributions to the beneficiaries effectively being first from current-year income to the extent that there is current-year income. If the amount distributed to the beneficiaries is less than the current-year income, the amount not distributed is taxable to the estate, not to the beneficiaries; the estate does not get a deduction for distributable net income that is not distributed.
