26 CFR 1.1402(a)-3: (a)-3 Special rules for computing net earnings from self-employment.

For the purpose of computing net earnings from self-employment, the gross income derived by an individual from a trade or business carried on by him, the allowable deductions attributable to such trade or business, and the individual's distributive share of the income or loss, described in section 702(a)(9), from any trade or business carrier on by a partnership of which he is a member shall be computed in accordance with the special rules set forth in §§ 1.1402(a)-4 to 1.1402(a)-17, inclusive.