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HMRC internal manual

National Insurance Manual

HM Revenue & Customs
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Class 4 NICs: computation of liability: summary


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).

This guidance relates to periods after the introduction of Self-Assessment. For guidance on earlier periods contact CTIS (Technical).

Guidance on deferment can be found in the National Insurance Deferment Manual.