Tax codes
If you've paid too much or too little tax
If you’re on the wrong tax code, you may pay too much or too little tax. You can get a refund or pay the tax you owe once HM Revenue and Customs (HMRC) has your income details for the tax year.
If you want a refund for anything other than a job or pension, check how to claim a tax refund.
If you’ve paid too much tax
When HMRC update your tax code, they check if they have all of your income details for the tax year.
If they do, they’ll work out the difference between how much tax you’ve paid and how much you should have paid.
They’ll ask your employer or pension provider to refund the difference in your pay. This will usually happen when they use your new tax code.
When your employer or pension provider gets your new tax code, if you’re paid:
- monthly - they should use it on your next pay or the following pay
- weekly - they should use it on your third pay
If HMRC do not have your details
You cannot get a refund until HMRC get your income details from your employer, pension provider or benefits office.
If you’ve changed jobs, give the P45 from your previous job to your new employer. If your previous employer did not give you a P45, ask them for one. This can give HMRC the details they need.
After the end of the tax year, HMRC get income details from employers, pension providers and the benefits office. HMRC will then:
- check how much tax you’ve paid
- send you a letter if you’ve not paid the right amount
- let you know how to get your refund, if you’ve paid too much
- update your tax code, if needed
If you have not paid enough tax
HMRC will:
- estimate how much tax you owe, when your tax code is updated
- adjust your tax code to collect the tax over one or more tax years, if possible
- check your tax after the end of the tax year and send you a letter if you’ve not paid the right amount
You’ll have an emergency tax code until the end of the tax year. In the new tax year, you’ll be put on a non-emergency tax code.