Common UK Tax Mistakes

What tax mistakes should you avoid? 

Tax can feel complicated, but many problems come from simple mistakes rather than complicated rules. 

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1. Ignoring your tax code 

Your tax code helps your employer calculate your Income Tax. 

 

If your income, job or circumstances change, an incorrect tax code could cause you to pay too much or too little. 

 

2. Not checking your payslip 

Check your: 

• gross pay; 

• Income Tax; 

• National Insurance; 

• tax code; 

• net pay. 

 

Spotting an unexpected deduction early is easier than discovering it months later. 

 

3. Forgetting about income outside your main job 

Income from: 

• tutoring; 

• freelancing; 

• online selling as a trader; 

• content creation; 

• other side hustles 

may create tax responsibilities. 

 

4. Missing Self Assessment deadlines 

If HMRC requires you to file a return, filing late can lead to penalties. (GOV.UK) 

 

5. Guessing figures 

HMRC expects people to take reasonable care to make sure tax returns and other documents are accurate. Careless or deliberate inaccuracies can result in penalties. (GOV.UK) 

 

Made a mistake? 

Do not panic or hide it. Self Assessment returns can normally be corrected within the permitted amendment period. (GOV.UK) 

 

Key takeaway 

Check your information, keep records and correct mistakes when you notice them.