Why Is My Second Job Taxed So Much?
When you start a second job, HMRC issues that employer a BR (Basic Rate) tax code. This tells the employer to deduct 20% Income Tax on every pound you earn — with no Personal Allowance applied. Your Personal Allowance (£12,570 in 2025/26) is assumed to be fully used by your main job.
This is not a penalty or a mistake. It reflects a fundamental fact: your Personal Allowance can only be used once. Because your main employer already applies it, your second employer must tax everything from the first pound. Your second job income sits on top of your main salary, so it is taxed at your marginal rate — the rate that applies to the next pound you earn.
If your main salary already takes you past the basic rate band (above £50,270), your second job income will be taxed at 40% or higher — even if the second job itself pays a relatively modest amount.
You can ask HMRC to split your Personal Allowance between your two employers if your main job income is below £12,570. This means some of your second job income would be tax-free. To do this, contact HMRC directly or update your tax code through your Personal Tax Account at gov.uk.
Tax on Second Job by Main Salary (2025/26 Reference)
The table below shows the marginal Income Tax rate on second job earnings, based on your main job income. Figures assume a standard Personal Allowance applied in full to the main job.
| Main Job Income |
Second Job Marginal Tax Rate |
| Under £12,570 |
0% (if remaining PA allocated to second job) |
| £12,571 – £50,270 |
20% (basic rate) |
| £50,271 – £125,140 |
40% (higher rate) |
| Above £125,140 |
45% (additional rate) |
Scottish taxpayers pay different rates. The calculator above applies Scottish rates automatically when the Scottish Taxpayer option is selected.
Worked Examples
£25,000 main job + £8,000 second job (BR code)
Second job gross£8,000
Tax codeBR (20%)
Income Tax on second job£1,600
NI on second job (own PT)£0
Net second job income£6,400
Effective rate on second job20%
£45,000 main job + £10,000 second job (BR code)
Second job gross£10,000
Tax codeBR (20%)
Income Tax on second job£2,000
NI on second job (own PT)£0
Net second job income£8,000
Effective rate on second job20%
£48,000 main job + £5,000 second job (crosses 40% band)
Second job gross£5,000
£2,270 at 20% (fills basic band)£454
£2,730 at 40% (into higher band)£1,092
Income Tax on second job£1,546
NI on second job (own PT)£0
Net second job income£3,454
Effective rate on second job~31%
NI: Each employer calculates National Insurance independently
Your second employer treats your second job as a separate employment for National Insurance purposes. This means your second job also has its own Primary Threshold (£12,570 per year). If your second job income is below £12,570, you will pay no NI on it at all — even though your main job income far exceeds the threshold. This is correct under the rules and not a loophole. However, it also means your combined NI position may differ from what you would pay if both incomes were assessed together.
Year-end reconciliation and P800 notices
At the end of each tax year, HMRC reviews your income from all sources. If the BR code caused you to pay too much or too little tax during the year, HMRC will issue a P800 tax calculation notice. If you overpaid, you will receive a refund. If you underpaid, HMRC will typically collect the balance through an adjusted PAYE tax code the following year. You should not normally need to file a Self Assessment return solely because of a second job, unless your total income exceeds £100,000 or you have other untaxed income.
Frequently Asked Questions
Can I use my Personal Allowance on my second job?
Not automatically. Your Personal Allowance is allocated to your main job by default. However, if your main job income is below £12,570, some of the allowance may be unused. You can contact HMRC to split the allowance between both employers — your second employer will then receive a different tax code (not BR) that reflects their portion of the allowance. Use your Personal Tax Account at gov.uk or call HMRC to arrange this.
Why does my second employer deduct 20% on everything?
Your second employer has been issued a BR (Basic Rate) tax code by HMRC. BR means no Personal Allowance is applied — tax is deducted at 20% from the first pound. This is the standard code for a second job because HMRC assumes your allowance is already in use elsewhere. If your main job earns above £50,270, your actual marginal rate is 40%, but the employer still deducts at 20% under BR. Any shortfall is collected by HMRC through a P800 adjustment or self-assessment.
Do I get a separate NI threshold for my second job?
Yes. Each employment is treated independently for National Insurance. Your second employer will apply the Primary Threshold (£12,570 per year / £1,047.50 per month in 2025/26) to your second job earnings separately. This means if your second job earns less than the threshold, you pay no employee NI on that income. This is different from Income Tax, where your marginal rate is determined by your combined income from all sources.
What is a P45 and why does my second employer need it?
A P45 is issued by your employer when you leave a job. It shows your total earnings and tax paid in the current tax year up to your leaving date. If you start a second job while keeping your main job, you will not have a P45 to give the new employer. In this case, your second employer should ask you to complete a Starter Checklist (previously called a P46). If you indicate it is a second job, the employer will apply the BR tax code. If you do not complete a checklist, the employer may use an emergency tax code (1257L W1/M1 or 0T), which may overtax you temporarily.
Do I need to do a self-assessment for a second job?
In most cases, no. If both jobs are PAYE employments and your combined income does not exceed £100,000, HMRC can manage your tax position through PAYE codes and year-end P800 adjustments. However, you must register for self-assessment if your total income from all sources exceeds £100,000, if you have income from self-employment over £1,000, or if you have other untaxed income such as significant rental income. If in doubt, check your obligations at gov.uk/self-assessment-tax-returns.
What happens if I leave my main job — does my second job become my main job?
Not automatically. Your tax code does not change just because you change jobs. When you leave your main job, your former employer will issue you a P45. You should give this to your remaining (formerly second) employer. That employer can then request an updated tax code from HMRC. Until HMRC issues a new code, the employer may continue to use BR or an emergency code. Contact HMRC directly to ask them to update your records and allocate your Personal Allowance to the new main employment as soon as possible.
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