Second job tax calculator
There is no “second job tax rate”. Your two incomes are added together and taxed once, the second job only feels heavily taxed because your £12,570 personal allowance is already used up by the first. This calculator shows the genuine combined position.
Of the £8,000 from your second job, you keep
£6,400.00
80% of it, £1,600.00 income tax and £0.00 National Insurance come off.
Why the second job feels heavily taxed
Your personal allowance is already used by the main job, so the second job is normally given a BR tax code: every pound taxed at 20% (or 40% if the two together push you over £50,270). But National Insurance works in your favour: each employment gets its own £12,570 threshold, so a second job under that pays no NI at all.
Common second-job mistakes
- Emergency code on the new job: until HMRC assigns BR, the second employer may over- or under-deduct. Check both codes in your tax code checker.
- Allowance on the wrong job: if the second job got your allowance and the main one got BR, you overpay. You can ask HMRC to split the allowance between jobs.
- Crossing into higher rate unnoticed: each employer only sees its own payroll; neither knows your combined income. If the total crosses a band, the underpayment surfaces later.
2026/27 rates, checked 2026-08-28. Assumes both jobs are employment (self-employed second income works differently). Method on the about page.