Circumstances in which a person entitled to child benefit is to be treated as if he were not so entitled

3.—(1) For the purposes of section 31 (child's special allowance), section 38 (guardian's allowance) or sections 41, 49 and 64(1) (benefit for beneficiary's dependent children) a person who is entitled to child benefit in respect of a child shall be treated as if he were not so entitled for—

(a) any period throughout which—

(i) that person, not being a parent of the child, does not fall to be treated as responsible for the child under section 3(1)(a) of the Child Benefit Act, and

(ii) a parent of that child falls to be treated as responsible for the child under the said section 3(1)(a); or

(b) any period throughout which—

(i) that person, not being a parent of that child, falls to be treated as responsible for the child under section 3(1)(a) of the Child Benefit Act, and

(ii) a parent of that child also falls to be treated as responsible for the child under the said section 3(1)(a); or

(c) any day following the day on which that child died.

(2) Sub-paragraph (b) of paragraph (1) shall not apply in the case of a person who is wholly or mainly maintaining the child referred to in that sub-paragraph.