Jargon-free personal tax calculator

A simple and quick way to calculate your tax bill that's officially recognised by HMRC. Calculate and file your tax return online, it's just £10 for Which? members, and £36 for non-members.  

Check your tax code

Tax errors occur mostly when people get the wrong tax code. 

This is normally because your circumstances have changed at some point during the year, or have become more complex, for example, having more than one job.

If you think you're not being taxed correctly, checking your tax code is the first thing you should do.

HMRC tax mistakes

If you're the victim of a HMRC error, generally you can claim a full rebate for the money you've lost.

This might depend on whether the money lost is akin to out-of-pocket expenses, which are easily identified and reimbursed, or something more obscure or difficult to prove, like loss of earnings or loss of business.

Find out how to complain about poor service or delays from HMRC in our handy step-by-step guide.

Your tax return mistakes

If you've paid too much tax because of a mistake on your tax return – for example by not claiming an allowance you were entitled to – you can correct your tax return within the first year of filing it.

After that you can still claim back tax within four years of the end of the tax year you’re claiming for, whether you are PAYE or self-assessment claimant.

Incorrect tax return penalties

There is a system of penalties for mistakes on your tax return, depending on whether HMRC thinks you've been careless or have tried to mislead them.

Incorrect tax penalties are based on the amount of tax you owe, and are payable in addition to the tax owed.

Which? tax calculator

Make sure the numbers add up. Answer a few short questions in our secure form to calculate your tax bill now with our Which? tax calculator.

Which? Money helpline

If you need expert advice or help with your tax return, the Which? Money Helpline has a qualified team of experts who can help with your query.

Using the Which? Money Helpline is a benefit for Which? members. You can sign up for a trial of Which? for £1.

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