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HMRC internal manual

National Insurance Manual

Class 4 NICs: Structure: Special Class 4 NICs: Calculation of Earnings

Regulation 105, SS(C)R 2001

Earnings for the purposes of special Class 4 NICs are the same as those for thepurposes of Class 1 NICs (see NIM02000 et seq).

However, the Class 4 NICs payable are calculated at the same percentage rates as ordinaryClass 4 NICs and not the equivalent Class 1 rates, see NIM24200.