Pay National Insurance when self-employed

If you are self-employed, you pay National Insurance in two ways. Class 4 is a percentage of your profits and is a tax: it does not count towards the State Pension or any benefit. Class 2 is a flat weekly contribution that builds your record, and you no longer have to pay it. HMRC works out both from your Self Assessment return, so you do not pay either separately during the year.

Class 4 National Insurance

You pay Class 4 on your taxable trading profits above the lower limit, whether or not you owe any income tax. The profits are those on your tax return after expenses and allowances. If you are a partner, you pay on your share. HMRC adds the Class 4 to your Self Assessment bill, and the same penalties and interest apply if you pay late.

You must file a return for HMRC to work out the amount. If you are employed as well as self-employed, your employer deducts Class 1 from your wages, and HMRC works out any Class 4 on your self-employed profits after you file, taking account of your combined earnings.

You may be able to claim a refund of Class 4 for earlier years. The rules change when you reach State Pension age.

Class 2 National Insurance

What happens with Class 2 depends on your profits for the tax year.

• If your profits reach the Small Profits Threshold, you are treated as having paid Class 2 for every week that you were self-employed. You pay nothing, and the year counts towards your State Pension and benefits.
• If your profits are below the threshold, you pay nothing unless you choose to. Without Class 2 for the year, you may have a gap in your National Insurance record.

Paying voluntary Class 2 is usually worth considering if your profits are low, because it is much cheaper than Class 3 and fills the gap in the same way for the State Pension. Check your State Pension forecast first, because an extra year is not worth buying if you already have enough qualifying years.

To pay voluntary Class 2 when you do not pay through Self Assessment, register with HMRC. HMRC then sends a payment request between September and the end of October, with an 18-digit reference number that you need to pay. You can usually pay for the past 6 tax years. If you miss the deadline on the payment request, you might have to pay more. Contact the National Insurance helpline if no request arrives by the end of November.

Some people are not treated as having paid Class 2 even when their profits are high, so they have to pay it themselves if they want the year to count. They are examiners, moderators and invigilators, ministers of religion who receive no salary or stipend, people who make investments for themselves or others other than as a business and without a fee or commission, and landlords who are eligible to pay Class 2. Examiners, moderators and invigilators also pay a special type of Class 4, which they arrange with the National Insurance office rather than through Self Assessment.

Class 3 National Insurance

Class 3 is a voluntary contribution for filling gaps that you cannot fill with Class 2, for example for years when you did not work. It counts towards the State Pension only. Check whether you can pay Class 2 before you pay Class 3, because Class 2 gives you the same State Pension year for far less.

Special rules apply if you live or work abroad. From 6 April 2026, you cannot pay voluntary Class 2 for time abroad, and you can pay Class 3 only if you have lived in the UK for 10 years in a row or paid 10 years of qualifying National Insurance contributions in total.

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