(a)(1) If a trust other than a foreign trust created by a U.S. person makes an accumulation distribution in any taxable year, the distribution is included in the beneficiary's gross income for that year to the extent of the undistributed net income of the trust for the preceding 5 years. It is therefore necessary to determine the extent to which there is undistributed net income for the preceding 5 years. For this purpose, an accumulation distribution made in any taxable year is allocated to each of the 5 preceding taxable years in turn, beginning with the most recent year, to the extent of the undistributed net income of each of those years. Thus, an accumulation distribution is deemed to have been made from the most recently accumulated income of the trust.

(2) If a foreign trust created by a U.S. person makes an accumulation distribution in any year after December 31, 1962, the distribution is included in the beneficiary's gross income for that year to the extent of the undistributed net income of the trust for the trust's preceding taxable years which began after December 31, 1953, and ended after August 16, 1954. It is therefore necessary to determine the extent to which there is undistributed net income for such preceding taxable years. For this purpose, an accumulation distribution made in any taxable year is first allocated to each of such preceding taxable years in turn, beginning with the most recent year, to the extent of the undistributed net income of each of those years. Thus, an accumulation distribution is deemed to have been made from the most recently accumulated income of the trust.

(3) If a trust that is in part a foreign trust created by a U.S. person and in part a foreign trust created by a person other than a U.S. person makes an accumulation distribution in any year after December 31, 1962, the distribution is deemed made from the undistributed net income of the foreign trust created by a U.S. person in the proportion that the total undistributed net income for all preceding years of the foreign trust created by the U.S. person bears to the total undistributed net income for all years of the entire foreign trust. In addition, such distribution is deemed made from the undistributed net income of the foreign trust created by a person other than a U.S. person in the proportion that the total undistributed net income for all preceding years of the foreign trust created by a person other than a U.S. person bears to the total undistributed net income for all years of the entire foreign trust. Accordingly, an accumulation distribution of such a trust is composed of two portions with one portion relating to the undistributed net income of the foreign trust created by the U.S. person and the other portion relating to the undistributed net income of the foreign trust created by the person other than a U.S. person. For these purposes, each portion of an accumulation distribution made in any taxable year is first allocated to each of such preceding taxable years in turn, beginning with the most recent year, to the extent of the undistributed net income for the applicable foreign trust for each of those years. Thus, each portion of an accumulation distribution is deemed to have been made from the most recently accumulated income of the applicable trust. If the foreign trust created by a U.S. person makes an accumulation distribution in any year after December 31, 1962, the distribution is included in the beneficiary's gross income for that year to the extent of the undistributed net income of the trust for the trust's preceding taxable years which began after December 31, 1953, and ended after August 16, 1954. If the foreign trust created by a person other than a U.S. person makes an accumulation distribution in any taxable year, the distribution is included in the beneficiary's gross income for that year to the extent of the undistributed net income of the trust for the preceding 5 years.

(b) If, before the application of the provisions of subpart D (section 665 and following), part I, subchapter J, chapter 1 of the Code, to an accumulation distribution for the taxable year, there is no undistributed net income for a preceding taxable year, then no portion of the accumulation distribution is deemed distributed on the last day of such preceding taxable year. Thus, if an accumulation distribution is made during the taxable year 1960 and the trust had no undistributed net income for the taxable year 1959, then no portion of the 1960 accumulation distribution is deemed distributed on the last day of 1959. For purposes of subpart D, the term 5 preceding taxable years includes only the 5 taxable years immediately preceding the taxable year in which the accumulation distribution is made and which are subject to part I (section 641 and following) of such subchapter J even though the trust has no undistributed net income during one or more of those years.

(c) Paragraphs (a) and (b) of this section may be illustrated by the following examples:

(d) For the purposes of allocating to any preceding taxable year an accumulation distribution of the taxable year, the undistributed net income of such preceding taxable year is computed without regard to the accumulation distribution of the taxable year or of taxable years following the taxable year. However, accumulation distributions of any taxable years intervening between such preceding taxable year and the taxable year are taken into account. Accordingly, if a trust has undistributed net income for the taxable year 1954 and makes an accumulation distribution during the taxable year 1955, the undistributed net income for 1954 is computed without regard to the accumulation distribution for 1955 or any subsequent year. If the trust makes a further accumulation distribution for 1956, the undistributed net income for 1954 is computed without regard to the accumulation distribution for 1956 or subsequent years; but in determining the undistributed net income for 1954 for purposes of the 1956 accumulation distribution the accumulation distribution for 1955 will be taken into account.