What Does K-codes Mean?
A K code means you have untaxed income (like a company car or unpaid tax from previous years) that exceeds your personal allowance. The number after K represents the amount of extra income to be taxed, divided by 10. For example, K500 means £5,000 of extra income needs taxing.
Is My Tax Code Correct?
If you think your tax code is wrong, you can check it on your payslip, through your HMRC online account, or by calling HMRC on 0300 200 3300. A wrong tax code means you're paying too much or too little tax.
All Common Tax Codes
| Code | Meaning |
|---|---|
| 1257L | £12,570 personal allowance |
| BR | All income taxed at 20% |
| D0 | All income taxed at 40% |
| D1 | All income taxed at 45% |
| NT | No tax deducted |
| 0T | No personal allowance |
| K-codes | You owe tax from elsewhere |
| W1 or M1 | Non-cumulative basis |
| S-prefix | Scottish income tax rates |
| C-prefix | Welsh income tax rates |
What K Means
A K code means your total allowances are less than your total deductions (from benefits in kind, tax owed, or state pension). The K code adds a notional amount to your taxable income rather than giving a tax-free amount. For example, K475 means £4,750 is added to your taxable income before calculating tax.
When This Code Is Used
K codes arise when the value of benefits (company car, medical insurance) or tax owed exceeds your Personal Allowance. They can also apply when you receive the State Pension alongside employment income. K codes cannot deduct more than half your pay in a single period — this is a legal protection.
Impact on Your Pay
A K code increases your tax bill compared to a standard code. If you have K475, your effective Personal Allowance is negative £4,750. On a £40,000 salary, you would be taxed as if earning £44,750, significantly increasing your tax deduction. Check your P11D to ensure the benefits in kind generating the K code are correct.
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Salary calculator →Learn more: Full guide to UK tax codes