A P800, also known as a tax calculation, is a letter from HMRC that tells you that you’ve paid the wrong amount of tax. You’ll get this by post.

A P800 can show you:

• If you paid too much tax: HMRC will tell you that you’ll get an income tax refund
• If you paid too little tax: don’t worry, HMRC will et you know about it and tell you how you can pay

In some cases, HMRC will send you a Simple Assessment form. It’s similar to the P800, and is issued in specific cases such as:

• Your sole income is through state pension
• You receive multiple sources of income

Bear in mind that at the time of writing, HMRC have halted issuing Simple Assessments.

What happens if I’m paying the wrong amount of tax?

As the P800 is an estimate, sometimes you are taxed incorrectly. There are several reasons why this can happen:

• You received an emergency tax code upon starting a new job
• You worked for part of the year or had multiple jobs
• Your employer used the wrong tax code
• You have multiple sources of PAYE income – such as pensions
• There is a change in your circumstances
• You receive benefits

I’ve received a P800, what’s next?

If you get a P800, you should check the details against HMRC with your P60, P45 and P11D forms, to make sure that there hasn’t been a mistake.

If you have multiple P800s, don’t worry. HMRC takes into account previous years’ figures. This means you’ll only have to worry about the most recent P800 you received.

Whilst it can be terrific news to get a P800 (i.e. HMRC owing you money 🎉), it can be alarming being told that you owe more tax. Don’t panic – the P800 is not an urgent tax demand. You have time to contact HMRC and double check.

What to do if:

• 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
• Your tax underpayment is more than £3,000 – HMRC will contact you about a special repayment schedule

Even if you haven’t received a P800, you can still claim a tax refund. You could still be owed tax from expenses that need to be declared to HMRC.