Last reviewed January 2023

A tax code is a string of numbers and letters that tells your employer how your earnings should be taxed. You get one for each Pay As You Earn (PAYE) job you have, and it’s important to keep track of them. Any time your tax code changes, HMRC will alter the Income Tax you’re paying each year.

If you’ve got a K tax code for your job, it means you’ve got some income factored into it that isn’t being taxed any other way, and it’s over your Personal Allowance threshold. There are a few reasons why this can happen. For example:

  • You might still owe tax from a previous tax year.
  • You might be getting state or company benefits that you need to pay tax on.