K tax code
UK tax glossary · Last reviewed: April 2026
K codes add income to your taxable pay, often because of taxable benefits or underpaid tax from earlier years. A K500 code adds £5,000 to taxable income.
K codes usually mean higher deductions — review your Personal Tax Account to understand why.
TaxHelper provides general information based on published HMRC rates and guidance. It is not regulated financial or tax advice. For decisions involving significant sums, complex circumstances, or if you are unsure, speak to a qualified accountant or HMRC directly.