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Class 4 national insurance contributions are paid by self-employed individuals (including partners in partnership) working in the UK¹. Class 4 contributions are calculated based on a percentage of the individual's trading profits and are reported and collected via the individual's self assessment tax return. Class 4 contributions are not deductible to any extent from business profits for income tax purposes².

For an overview of Class 4 contributions, see E8.316. For the rate of Class 4 contributions, see E8.318.

The self-employed may also be liable to pay Class 2 national insurance contributions, which are a weekly contribution also collected via the self assessment return³. See E8.301.

This article explains how to calculate the maximum Class 4 contributions payable where a person is employed and self-employed in the same tax year.

Note that from 2015/16 onwards it is no longer possible to defer Class 4 contributions. Before this date it was an individual who was both employed and self-employed could apply for a certificate to defer Class 4 contributions where it was