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The P800 form: what to do if HMRC sent you one

  • 2 min read
  • Last updated 12 Feb 2021

A P800 form, also known as a tax calculation, is a letter that HMRC will send you when they think that you have not paid the right amount of tax:

  • either too little
  • or too much tax.

What if I think that my P800 form is wrong?

It can happen – P800s aren’t always correct.

What you need to do:

  1. Compare it with your P60P45, and P11D forms
  2. Check that HMRC included your flat rate job expenses (uniform laundry allowance, etc.)
  3. Check that HMRC also included your regular job expenses (mileage allowances, professional subscription fees, parking fees, business phone call, travel and overnight costs, etc.)
  4. Also check for adjustments like the married couples’ allowance, etc.

What can happen:

  • your P800 is correct – you don’t need to do anything
  • you overpaid tax – HMRC will refund you within 4 weeks
  • you underpaid tax, but it’s less than £3,000 – HMRC will collect the tax directly through your tax code
  • or you underpaid tax, and it’s more than £3,000 – HMRC will contact you about a special repayment schedule.

It says I can get a tax refund. How do I get it?


What you need to do:

  1. Go to the HMRC website
  2. Sign in to your Personal Tax Account using your Government Gateway User ID
  3. Follow the steps to request a refund.

Once you finished, you should receive the rebate to your bank account in about 5 days.

By phone

You can also call HMRC on 0300 200 3300.

Wait for a cheque

If you don’t do anything, HMRC will send you a cheque within 14-45 days from the date on your P800.

What if my P800 says I owe tax?

HMRC will either collect it through your PAYE tax code or ask you to pay directly.

What if I have P800s from multiple years?

Each form includes the previous years, so you only need the one from the final year.

I didn’t get one. Can I still claim a tax refund?

Short answer: yes.

You could still be owed tax from expenses that the HMRC doesn’t know about.

For example, if you work in construction, you might want to claim the mileage allowance.

Let us know if you need help.

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