SolvedNIM24600 | Class 4 NICs: computation of liability: summary
From HM Revenue & Customs · National Insurance Manual
Section 15 of the Social Security Contributions and Benefits Act 1992
The following sections look at the computation of the Class 4 NICs profits.
The self-employed pay Class 4 NICs on profits immediately derived from the carrying on of a trade, profession or vocation (SSCBA92/S15) but only where those profits are chargeable to Income Tax under Chapter 2 of Part 2 to the Income Tax Trading and Other Income Act 2005 (ITTOIA).