More UK workers than ever are taking on a second job whether to supplement their main income, pursue a passion project, or navigate the rising cost of living. But second jobs carry important tax implications that are frequently misunderstood. Many second-job earners overpay tax for months without realising it, while others unknowingly underpay and face unexpected bills from HMRC. This comprehensive AccFirm guide covers everything you need to know about second job tax in the UK for 2025/26.
How Is a Second Job Taxed in the UK?
In the UK, every individual gets just one Personal Allowance £12,570 for 2025/26 regardless of how many jobs they hold. This is the fundamental rule that shapes second job taxation. When you have two jobs:
- Your main job claims your full Personal Allowance (tax code 1257L)
- Your second job has no Personal Allowance applied to it
- Income from your second job is taxed from the first pound using a BR, D0, or D1 tax code
This is not a special penalty for having two jobs it is simply the result of having already used your personal tax-free allowance on your primary income source.
What Tax Code Will I Have on My Second Job?
HMRC typically assigns one of the following codes to a second job:
| Tax Code | Rate Applied | When Used |
| BR | 20% (Basic Rate on all income) | Most common for second jobs — basic rate taxpayer |
| D0 | 40% (Higher Rate on all income) | Second job income falls in higher-rate band due to combined income |
| D1 | 45% (Additional Rate on all income) | Combined income exceeds £125,140 |
| 0T | Progressive rates with no allowance | Sometimes used in complex situations |
The BR code means every pound you earn from your second job is taxed at 20%, starting from the first pound. This can feel like paying a lot of tax on your second income but it is correct if your main job already uses your full Personal Allowance.
Why Might You End Up Paying Too Much Tax on a Second Job?
The most common cause of overpaying tax on a second job is being placed on an emergency tax code (e.g. 1257L W1 or M1) rather than the correct BR code. When you start a second job:
- Your new employer needs your P45 from the second job (usually “not applicable” if it’s a new role, not a leaving job)
- You should complete a starter checklist indicating this is a second job (Statement B or C)
- Without the correct information, your employer may apply an emergency code that overtaxes you
HMRC will typically correct this automatically after receiving Real Time Information (RTI) from both employers. However, this can take weeks or months. In the meantime, you will be overpaying tax.
How Much Tax Will I Pay on a Second Job?
The amount of tax you pay on second-job income depends entirely on your combined income from both jobs:
Scenario 1: Combined Income Remains Below £50,270
If your main salary is £30,000 and your second job pays £10,000, your combined income is £40,000. Both are within the basic rate band. Your second job income is taxed at 20% (BR code), with no Personal Allowance. You pay £2,000 in Income Tax on the second job.
Scenario 2: Combined Income Crosses the £50,270 Threshold
If your main salary is £45,000 and your second job pays £12,000, your combined income is £57,000. The first £50,270 falls within the basic rate band; the remaining £6,730 is taxed at 40% (higher rate). On your second job alone, you would pay: 20% on the first portion (up to the higher-rate threshold), then 40% on any income above the threshold.
Scenario 3: Distributing the Personal Allowance
If your main job income is very low (for example, you work part-time earning £8,000), you may have unused Personal Allowance. You can contact HMRC to split your Personal Allowance between your two jobs, reducing the tax on both income sources. HMRC does not do this automatically you must request it.
National Insurance on a Second Job
Unlike Income Tax, National Insurance is calculated separately on each job’s income they are not combined. For 2025/26:
- You pay 8% NI on earnings between £12,570 and £50,270 in each job independently
- If both jobs pay above the Primary Threshold (£12,570), you will pay NI on both
- You cannot overpay NI across two jobs in the same way as Income Tax each job is assessed separately
- If your combined NI contributions exceed the maximum for the year (based on the Upper Earnings Limit), you may be entitled to a refund via Self Assessment
Self-Employment as a Second Income: Key Tax Rules
If your “second job” is self-employment freelancing, contracting, driving for a delivery platform, or running a side business the tax treatment is different from employed second job income:
- Trading Allowance: The first £1,000 of self-employment income per tax year is tax-free (no need to register or declare)
- Registration: If self-employment income exceeds £1,000, you must register for Self Assessment and file a tax return
- Tax: Self-employment profits are added to your employment income and taxed at your marginal rate (20%, 40%, or 45%)
- National Insurance: Self-employed individuals pay Class 4 NI (9% on profits between £12,570 and £50,270, then 2% above) and were formerly subject to Class 2 NI (now abolished from April 2024)
- Expenses: You can deduct allowable business expenses from self-employment income before tax
Do I Need to File a Self Assessment Tax Return with Two Jobs?
If both your jobs are employed (PAYE), you generally do not need to file a Self Assessment tax return unless:
- Your combined income from all sources exceeds £100,000 per year
- You have any untaxed income, including income from self-employment, property, or savings above your allowances
- You claim certain reliefs (such as higher-rate pension relief) that cannot be processed through PAYE
- HMRC sends you a notice to file a tax return
How to Avoid Overpaying Tax on a Second Job
Here are AccFirm’s top tips to avoid overpaying tax when working two jobs:
- Complete the starter checklist correctly: When starting a second employed job, clearly indicate on the checklist that you have another job. This triggers the BR code rather than an emergency code.
- Split your Personal Allowance: If your main job income is low, contact HMRC to request your allowance be divided between both employers phone 0300 200 3300.
- Check your tax codes each year: Review codes on both payslips. Your main job should show 1257L and your second job should show BR (or appropriate higher-rate code).
- File Self Assessment if required: If your combined earnings have resulted in untaxed income or you need to claim reliefs, register and file a return.
- Act quickly if codes are wrong: If both jobs are showing 1257L, you are being under-taxed and will face a bill later. Contact HMRC immediately.
Second Job Tax for Directors
If you are employed at one company and are also a director of your own limited company, you have two sources of income: your employment salary and your director’s salary and dividends. This creates a complex tax situation that requires careful planning:
- The director’s salary and dividends are separate from your employment income
- Combined income determines your tax band for all sources
- Dividends are taxed at 8.75% (basic rate), 33.75% (higher rate), or 39.35% (additional rate) above the £500 Dividend Allowance (2025/26)
- Self Assessment is mandatory for all directors receiving company income
AccFirm specialises in director tax planning ensuring the optimal salary and dividend split to minimise your overall tax liability within HMRC rules.
Frequently Asked Questions: Second Job Tax UK
Why am I paying 20% tax on my second job?
This is correct if your main job has already used your £12,570 Personal Allowance. The BR tax code taxes all second-job income at 20% basic rate from the first pound. You are not being penalised your allowance is simply being used elsewhere.
Can I claim my Personal Allowance on my second job?
You have one Personal Allowance per tax year and it is applied first to your main source of income. If your main income is below £12,570, you have unused allowance that can be transferred to your second job contact HMRC to request this.
Do I pay National Insurance on a second job?
Yes NI is assessed on each employment separately, not combined. You will pay NI on second-job earnings above the Primary Threshold (£242 per week / £1,048 per month in 2025/26).
What if I start a second job mid-year?
Starting a second job mid-year does not create any specific tax complication beyond the normal second-job rules. Ensure you complete the starter checklist correctly and monitor your tax codes on both payslips.