What does kx tax code mean

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Last updated: April 4, 2026

Quick Answer: The 'KX' tax code, also known as the 'K' code, indicates that you have exceeded your personal allowance and are therefore liable for income tax on all your earnings. This means that no tax-free personal allowance is being applied to your income for the current tax year.

Key Facts

The KX tax code means your personal allowance has been used up.
You will pay tax on all income earned while this code is active.
It's often applied when you have multiple jobs or significant untaxed income.
This code is temporary and can be updated if your circumstances change.
It is essential to review your payslips to understand why this code is applied.

What is a Tax Code?

In the UK, a tax code is a set of numbers and letters that tells your employer or pension provider how much tax-free income you are allowed each year. It's used to calculate how much income tax should be deducted from your wages or pension. The most common tax code for employed individuals is 1257L, which means you can earn £12,570 tax-free in the current tax year (2023-2024). The 'L' signifies that you are entitled to the standard tax-free Personal Allowance.

Understanding the 'KX' Tax Code

The 'KX' tax code, often referred to as a 'K' code, signifies a specific situation where your entitlement to a tax-free Personal Allowance has been entirely used up or is no longer applicable for the current tax year. When you see 'KX' on your payslip, it means HMRC (Her Majesty's Revenue and Customs) has instructed your employer to deduct tax from every pound you earn, with no allowance for tax-free income.

Why Might You Receive a 'KX' Tax Code?

There are several common reasons why you might be issued with a 'KX' tax code:

Multiple Income Sources: If you have more than one job, or receive income from sources other than your main employment (like rental income, significant savings interest, or dividends) that, when combined with your employment income, exceed your total Personal Allowance, HMRC might issue a 'KX' code to ensure tax is collected correctly. In such cases, your Personal Allowance might be allocated to one job, and the other income will be taxed via a 'KX' code.
Benefits or Allowances Received: If you have received benefits or allowances from HMRC that are taxable, and the value of these benefits exceeds your standard Personal Allowance, you might be put on a 'KX' code. For example, if you received a significant taxable benefit from an employer.
Arrears in Tax Payments: In some situations, if you owe a significant amount of tax from previous years, HMRC might decide to collect this through your current income by applying a 'KX' code. This effectively means you're paying off the arrears by having tax deducted from all your earnings.
Unusual Circumstances: Occasionally, a 'KX' code might be applied due to administrative errors or unusual circumstances that require clarification with HMRC.

What Does 'KX' Mean for Your Take-Home Pay?

The direct impact of a 'KX' tax code is a reduction in your net take-home pay. Since no Personal Allowance is being applied, the tax deducted from your gross earnings will be higher. For example, if your gross salary is £2,000 per month, under a standard code like 1257L, a portion of this would be tax-free. However, with a 'KX' code, tax will be calculated on the full £2,000.

What Should You Do if You Have a 'KX' Tax Code?

If you find a 'KX' tax code on your payslip, it's crucial to take action:

Check Your P45/P60: Ensure that the information on your P45 (from a previous employer) or P60 (annual summary from your current employer) is accurate and reflects your earnings and tax paid correctly.
Contact HMRC: The most important step is to contact HMRC directly. They can explain precisely why the 'KX' code has been issued. You can usually do this by phone or through your personal tax account online. Be prepared to provide details about all your sources of income and any benefits you receive.
Review Your Income: Assess all your income streams. If you have multiple jobs or significant untaxed income, this might be the reason for the 'KX' code.
Seek Professional Advice: If you are unsure about the implications or the reasons for the 'KX' code, consider consulting a tax advisor or accountant. They can help you understand your tax situation and liaise with HMRC on your behalf.

Is the 'KX' Code Permanent?

No, a 'KX' tax code is typically not permanent. It is usually applied for a specific tax year or until the circumstances that led to its issuance are resolved. Once your tax situation changes, or you have paid off any outstanding tax liabilities, HMRC will update your tax code accordingly. It's essential to keep HMRC informed of any changes to your employment or income sources.

Distinction from Other 'K' Codes

It's worth noting that 'KX' is the most common 'K' code, but there can be other 'K' codes (e.g., K100, K200). These codes indicate that the amount of income on which you are taxed is the stated amount multiplied by 10, or 100, etc., in addition to the income on which you are taxed normally. The 'KX' code specifically means that your entire Personal Allowance has been used up, and tax is applied to all your income.

In summary, while a 'KX' tax code can be alarming due to its impact on your take-home pay, understanding its meaning and taking proactive steps to clarify the situation with HMRC will help ensure your tax affairs are managed correctly.