National Insurance Class 4 UK

Overview

Calculate National Insurance Class 4 UK using the official rates and regulations for United Kingdom.

How it works

Enter the base amount and the calculator will apply the relevant rates and brackets to compute the result.

Understanding Class 4 National Insurance for Self-Employed Profits

Class 4 National Insurance is a tax on the profits of self-employed individuals and partners in partnerships, calculated and collected through the Self Assessment system. For the 2025-26 tax year, the rates are 6% on profits between the Lower Profits Limit of £12,570 and the Upper Profits Limit of £50,270, and 2% on profits above £50,270. Unlike Class 2, which provides state pension entitlement, Class 4 is purely a revenue-raising contribution with no direct benefit entitlement attached. The combined effect of Class 2 reform and Class 4 means that a self-employed person earning £40,000 pays approximately £1,646 in Class 4 NI plus income tax of approximately £5,486, for a total tax and NI bill of approximately £7,132, compared to approximately £8,406 for an employee earning the same amount through PAYE. The self-employed therefore pay less NI overall, though they do not receive statutory sick pay, statutory maternity pay, or employer pension contributions that employees receive. Understanding this trade-off is essential when deciding between employment and self-employment, as the apparent tax saving must be weighed against the loss of employment benefits and protections.

Calculating Class 4 NI on Partnership and Multiple Income Sources

For partners in partnerships, Class 4 NI is calculated on each partner's share of the partnership profits rather than the total partnership income. This means that a partnership with £200,000 in profits split equally between four partners results in each partner being assessed on £50,000, with each paying Class 4 on their individual share. If you have multiple self-employment income sources, the profits are aggregated for Class 4 purposes, meaning two separate businesses with profits of £30,000 each result in Class 4 being charged on £60,000 total, not £30,000 separately. Losses from one self-employment can be offset against profits from another for Class 4 purposes, and trading losses can also be carried forward against future profits from the same trade. The calculation is performed on your Self Assessment tax return, and HMRC may open an enquiry if the reported profits appear inconsistent with lifestyle indicators or information received from third parties.

Planning Strategies to Minimise Class 4 Liabilities

Several legitimate strategies can reduce Class 4 NI liability. Incorporation transfers profits from self-employment to a limited company, replacing Class 4 NI with corporation tax at 19-25% and dividend tax at 8.75-39.35%, which can be more efficient for profits above approximately £30,000-40,000 depending on personal circumstances. However, incorporation introduces additional administrative costs and compliance obligations including annual accounts, corporation tax returns, and Companies House filings. Pension contributions reduce both income tax and Class 4 NI by lowering adjusted profits, with the annual allowance of £60,000 providing substantial scope for tax-efficient retirement saving. Capital allowances on equipment purchases reduce trading profits for both income tax and Class 4 purposes, with the Annual Investment Allowance providing 100% relief on up to £1 million of qualifying expenditure. Our calculator helps you model the NI impact of different profit levels and strategies, comparing self-employment with incorporation to identify the optimal structure for your business.

Using Our Class 4 NI Calculator

Our Class 4 NI calculator computes the exact National Insurance liability on self-employment profits at the current 6% and 2% rates. Enter your trading profits after expenses but before tax to see the Class 4 charge alongside income tax, giving a complete view of your self-employment tax obligations. The calculator also models the impact of pension contributions, capital allowances, and trading losses on your Class 4 liability, and compares the total tax and NI position of self-employment against incorporation at your profit level. This comparison is invaluable for self-employed workers considering whether to form a limited company, showing the precise financial difference between the two structures based on your actual circumstances.

Our calculator provides the clarity needed to plan your self-employment tax strategy, whether you are estimating payments on account, considering incorporation, or simply understanding your total tax and NI obligation for the current year.

Understanding how Class 4 NI interacts with income tax and Class 2 entitlement provides a complete picture of your self-employment tax obligations, enabling better financial planning and more informed decisions about business structure and profit extraction strategies.