Advanced options
What The National Insurance Calculator Works Out
- Employee NI per year: 8% of earnings between the primary threshold of GBP 12,570 and the upper earnings limit of GBP 50,270, plus 2% of everything above. A GBP 35,000 salary pays about GBP 1,794 a year; GBP 60,000 pays about GBP 3,211.
- Per month / week: the annual figure divided by 12 and 52, assuming steady pay. NI is calculated per pay period rather than cumulatively, so uneven pay changes the total.
- Effective NI rate: NI as a percentage of the whole salary. The marginal rate falls from 8% to 2% exactly where income tax rises from 20% to 40%, so combined marginal deductions run 28% for basic-rate earners and 42% above the limit, before student loans.
- NI category letter (advanced): most employees are category A. Under-21s (M) and apprentices under 25 (H) pay the same but their employer pays nothing up to GBP 50,270; married women with a pre-1977 election (B) pay a reduced 1.85%; and NI stops entirely at State Pension age (C) even if you keep working.
- Employer NI per year (advanced): the employer's own Class 1 contribution, 15% of pay above GBP 5,000, which never appears on your payslip but is part of what you cost. Small employers can offset up to GBP 10,500 a year through the Employment Allowance.
- NI in the bonus pay period (advanced): because thresholds are applied per week or month, a bonus is charged in the period it lands. A bonus paid to someone already above the monthly upper limit attracts only 2%, while one that lifts a lower earner through the band costs 8%, and unlike income tax it is never reconciled at year end.
- NI saved by salary sacrifice (advanced): sacrificed pay escapes both employee and employer NI as well as income tax, which is why pension salary sacrifice beats an ordinary contribution by 8% below the upper limit and 2% above. The employer's saving is shown too, since the better schemes pass some or all of it into the pension.
- Class 4 if self-employed (advanced): the same sum taken as self-employed profit pays 6% between GBP 12,570 and GBP 50,270 and 2% above, through self assessment, and Class 2 is now credited free above the small profits threshold. The gap against employee NI is one reason contracting looks cheaper on paper.
- What NI buys: each qualifying year counts toward the 35 needed for a full new State Pension. Gaps can be filled with credits (for parents and carers) or voluntary Class 3 payments, which are often the best-value purchase available to someone approaching retirement short of 35 years. Not tax advice.
Source and further reading: GOV.UK (HMRC): National Insurance rates.