Tax codes

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Why your tax code might change

HM Revenue and Customs (HMRC) change your tax code if you need to pay a different amount of tax.

This usually happens when your income or circumstances change, for example if:

If you start a job and your new employer does not know your previous income details, you may be put on an emergency tax code.

If your tax code has changed, you can use the Check your Income Tax online service to find out why.

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This page is Part of Start a new job: step by step

  1. Step 1 Get your National Insurance number

    You'll need your National Insurance number to start your new job.

    1. Find your National Insurance number
    1. Apply for a National Insurance number if you do not already have one

  2. Step 2 Accept the job offer

    The offer might be ‘conditional’ or ‘provisional’, which means you may need to give further details to your new employer or pass pre-employment checks.

    1. Find out about your rights when accepting a job offer

  3. Step 3 Share your details for any employer checks

    Give your new employer what they need to complete any pre-employment checks.

    1. Find out what checks your employer can make
    1. Find out how to prove your right to work
    1. Find out about criminal record checks

  4. Step 4 Review your employment contract

    Your new employer should give you an employment contract. Check the terms before you agree to it.

    1. Find out about employment contracts

  5. and If you're leaving a job, hand in your notice

    Tell your current employer that you’re going to leave and when your last day will be. This is known as handing in your notice.

    1. Find out how to hand in your notice

    When you hand in your notice, ask your employer when you’ll get your P45.

    1. Find out about the P45

  6. Step 5 Prepare your personal information for your first day

    To get paid, you’ll need to give your new employer:

  7. Step 6 Give your P45 to your new employer

    Your new employer will use your P45 to work out how much tax to take from your pay.

    1. Find out about the P45

  8. or If you do not have a P45, fill in the starter checklist

    Use the starter checklist to give your employer details they need to work out your pay and tax.

    1. Fill in the starter checklist

  9. Step 7 Check your first payslip

    Your employer must give you a payslip on or before payday.

    1. Find out what should be on your payslip

    It’s your responsibility to make sure you’re paying the right amount of tax.

    1. Check if the tax on your payslip is correct

    If you think the tax is wrong, your tax code may be incorrect.

    1. Find out what to do if you think your tax code is wrong