Last updated 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 been given a D0 tax code, it basically means you’re being taxed at the higher rate of Income Tax (40%) on all of your income from this job, without the benefit of a tax-free Personal Allowance!

The chances are, this has happened because you’ve got more than one job and your Personal Allowance is linked to the other one. It also means you’re earning enough to pay Income Tax at the 40% higher rate.