(a) General rule. Except as provided inparagraph (b) of this section, net in-vestment income does not include any item taken into account in deter-mining self-employment income that is subject to tax under section 1401(b) for such taxable year. For purposes of sec-tion 1411(c)(6) and this section, taken into account means income included and deductions allowed in determining net earnings from self-employment.However, amounts excepted in deter-mining net earnings from self-employ-ment under section 1402(a)(1)–(17), and thus excluded from self-employment income under section 1402(b), are not taken into account in determining self-employment income and thus may be included in net investment income if such amounts are described in § 1.1411–4. Except as provided in paragraph (b) of this section, if net earnings from self-employment consist of income or loss from more than one trade or busi-ness, all items taken into account in determining the net earnings from self-employment with respect to these trades or businesses (see § 1.1402(a)–2(c)) are considered taken into account in determining the amount of self-em-ployment income that is subject to tax under section 1401(b) and therefore not included in net investment income.