Tax code calculators
K tax code calculator
The number after the K is an amount added to your pay before tax: what it costs on each payslip and where the limit stops it.
Tax each month with K475
£379.20
£4,750 a year is added to your pay before tax.
| Added to pay each month | £396.59 |
| Taxable pay | £1,896.59 |
| Half of the pay (limit) | £750.00 |
| Tax over the year | £4,551.80 |
Tax the limit stops at the end of the year is a matter between you and HMRC: it is not carried on your P60.
A tax code starting with K means HMRC has found more untaxed income, benefits or deductions to collect than your whole tax-free allowance, so the code works in reverse: instead of free pay, an amount is added to your pay before tax is worked out. The number is that amount without its last digit: K475 adds £4,750 over the year. GOV.UK lists the usual reasons: tax owed from an earlier year collected through your wages or pension, the State Pension or taxable benefits paid without tax, company benefits such as a car, or savings interest above your Personal Savings Allowance (K in your tax code). On a monthly payroll, K475 adds £396.59 to each month's pay; with £1,500 a month it takes £379.20 in tax. The tax taken in any one pay can never exceed 50% of that pay. SK and CK are the Scottish and Welsh versions.
K code: tax and the 50% limit
Tax this month
£380.00
| Added to pay | £1,000.76 |
| Limit: half the pay | £450.00 |
| Not taken because of the limit | £0.00 |
Rules read on HMRC’s texts by Radif Partners · Editorial policy · Method
What the number after the K adds
For a normal code, the number times ten is the allowance. For a K code, the number times ten is the amount by which the items HMRC collects exceed the allowance. If your allowance is £12,570 and HMRC must collect tax on £17,320 of benefits and State Pension through this job, the difference of £4,750 becomes K475. Payroll software turns it into an amount per period with the same table as free pay: the number times ten plus nine, divided by 12 or 52, rounded up (PAYE specification).
| Code | Added over the year | Added each month | Tax on £1,800 in month 1 |
|---|---|---|---|
| K100 | £1,000 | £84.09 | £376.80 |
| K475 | £4,750 | £396.59 | £439.20 |
| K1000 | £10,000 | £834.09 | £526.80 |
| K2000 | £20,000 | £1,667.43 | £758.46 |
The 50% limit, in practice
Under a K code, no payroll may deduct tax worth more than 50% of the gross pay or pension for the period (GOV.UK). Payroll applies it pay by pay: if the tax worked out is higher than half of that pay, the deduction stops at half. On a cumulative code, the remainder is carried forward and taken later when your pay leaves room. A pensioner with a small workplace pension and a large State Pension is the typical case: the State Pension, paid without tax, can make the K amount larger than the pension itself.
K code: tax and the 50% limit
Tax this month
£300.00
| Added to pay | £1,667.43 |
| Limit: half the pay | £300.00 |
| Not taken because of the limit | £153.40 |
Why HMRC uses a K code
The code collects tax on income that has no tax taken off at source, through the one payment that does. Company benefits such as a car and fuel, medical insurance or a loan are reported by your employer and taxed through the code (tax on company benefits). The State Pension is paid gross, so its tax is collected from a workplace pension or a job. An underpayment from an earlier year, or a Self Assessment bill under the coding out limit of £3,000, is added too. When these items together pass your allowance, the code turns into a K.
Reading a K code on your payslip and in your account
Your payslip shows only the code, for example K475 or SK475. The breakdown is in your HMRC online account and on any coding notice: the Personal Allowance at the top, then each deduction with its amount, then the total that turns negative. Check each line against what you know. A car you no longer have, a pension counted at the wrong weekly rate, or an estimate of untaxed interest that is far above what your bank paid are the usual errors. Correcting the line changes the number, and HMRC sends the new code to the payroll within 15 working days.
A K code on its own is not a sign of a mistake. If the items are right, it simply makes sure the tax on them is paid through the year instead of arriving as a bill after 5 April. The cumulative method also means that if the code changes during the year, the next payslip corrects the tax for the months already paid.
The right code checker takes your benefits and State Pension and shows whether a K code is what your figures point to. The company benefits page and the underpaid tax page explain each source of a K code, and the State Pension page the pensioner's case.