UK Tax Code Checker

A UK tax code is a combination of numbers and letters issued by HMRC that tells your employer or pension provider how much Income Tax to deduct from your pay. It determines your tax-free Personal Allowance and ensures the correct amount of tax is collected throughout the tax year (6 April to 5 April). An incorrect tax code could mean you're overpaying or underpaying tax, so it's important to check yours regularly.

1257L is the standard tax code for the 2024/25 tax year. The numbers "1257" multiplied by 10 give you a tax-free Personal Allowance of £12,570. The letter "L" means you're entitled to the standard Personal Allowance with no special adjustments. If you have one job and no additional income sources, this is likely your code.

These are flat-rate tax codes typically used for second jobs or pensions:

• BR — Basic Rate (20%) on all income from this source. No Personal Allowance applied.
• D0 — Higher Rate (40%) on all income. Used when your main income already uses the basic rate band.
• D1 — Additional Rate (45%) on all income. For very high earners with multiple income streams.

These codes mean you have no tax-free allowance on that particular job or pension.

A K code (e.g., K475) means your total deductions and taxable benefits exceed your Personal Allowance. Instead of reducing your taxable income, the number (multiplied by 10) is added to your taxable pay. For example, K475 means £4,750 is added to your taxable income. K codes often arise from company benefits like a car, medical insurance, or underpaid tax being collected through your wages. HMRC ensures the additional tax collected never exceeds 50% of your gross pay.

W1 (Week 1) and M1 (Month 1) are non-cumulative or "emergency" indicators. They mean your tax is calculated on each pay period in isolation, without considering your year-to-date earnings. This can lead to overpayment of tax, especially if you started a job mid-year. X is a similar emergency marker. These are often applied when HMRC lacks full information about your income. Once your details are updated, your employer should switch you back to a cumulative code.

S prefix (e.g., S1257L) means you're a Scottish taxpayer and Scottish Income Tax rates apply. Scotland has six tax bands (Starter 19%, Basic 20%, Intermediate 21%, Higher 42%, Advanced 45%, Top 48%) compared to England's three. C prefix (e.g., C1257L) identifies Welsh taxpayers. Since April 2019, the Welsh Government can set its own rates, though for 2024/25 they remain aligned with England and Northern Ireland. Both prefixes ensure the correct devolved rates are applied.

M code (e.g., 1383M) means you're receiving the Marriage Allowance — your spouse or civil partner has transferred 10% of their Personal Allowance (£1,260 for 2024/25) to you, increasing your allowance to around £13,830. N code (e.g., 1131N) means you've transferred 10% of your allowance to your partner, reducing yours to about £11,310. Marriage Allowance is only available when the recipient is a basic-rate taxpayer and the transferor earns below the Personal Allowance threshold.

NT stands for "No Tax." No Income Tax will be deducted from this source of income. This is rare and typically applies to individuals like charities, certain non-resident performers, or specific international agreements. It does not mean no tax is owed overall — it simply means this particular payer does not deduct tax. You should confirm with HMRC if you receive an NT code unexpectedly.

HMRC reviews tax codes annually before the start of each tax year (April). You may also receive a new code mid-year if your circumstances change — such as changing jobs, receiving a company benefit, or underpaying/overpaying tax. You should check your tax code:

• At the start of each tax year
• When you change jobs
• If your income changes significantly
• If you receive a P800 or Simple Assessment letter
• Whenever you notice unexpected changes to your take-home pay

If you believe your tax code is incorrect:

1. Check your code against your payslip and any HMRC correspondence (P2 coding notice).
2. Use HMRC's online check tool or log into your Personal Tax Account at GOV.UK.
3. Contact HMRC directly on 0300 200 3300 with your National Insurance number and P60/P45 ready.
4. Inform your employer — they can only change your code when instructed by HMRC.

You may be entitled to a tax refund if you've overpaid due to an incorrect code.

A T code (e.g., 1257T) means HMRC needs to review other elements of your tax calculation before finalising your code. It's a temporary or review code, often used when your tax affairs are more complex — for example, if you have multiple income sources, significant savings interest, or are self-employed alongside PAYE employment. The number still represents your estimated allowance divided by 10, but the final calculation may differ. Monitor your tax code notices closely if you're on a T code.

Many factors can reduce or adjust your tax code below the standard 1257L:

• Taxable benefits — company car, private medical insurance, accommodation
• Underpaid tax from previous years being collected through your current wages
• Multiple jobs — your allowance is usually applied to just one job
• State Pension or other untaxed income reducing your available allowance
• High income — Personal Allowance tapers away above £100,000 (losing £1 per £2 earned)

Each of these reduces the number in your tax code accordingly.