Register for tax and avoid a penalty

You need to tell HM Revenue & Customs (HMRC) about these or any other changes that mean you have to register for a particular tax or pay tax on undeclared income.

Under regulations that took effect from 1 April, you could pay a penalty as well as the tax you owe if you don’t tell HMRC at the right time that:

  • You’re liable to tax because your new business has made a profit;
  • your business’s turnover has reached the VAT registration threshold;
  • you sell an asset and make a capital gain on which tax should be paid; or
  • you have any income that isn’t taxed and you haven’t declared it.

What could it cost?

The new penalty for failing to tell HMRC about taxable income is a percentage of the tax that you owe. You may pay a higher penalty if you deliberately fail to tell HMRC about your income – and an even higher penalty if you take steps to hide it.

The amount you will pay depends on how HMRC views your actions: 

  • not deliberate – the penalty is between 0 and 30 per cent of the tax you owe;
  • deliberate but without concealment –  20 to 70 per cent of the tax owed; or
  • deliberate with concealment – 30 to 100 per cent of the tax owed.

The amount of the penalty will also depend on how much help you give HMRC. If you provide access to your records and help HMRC calculate what tax is due, the amount will be reduced.

HMRC can reduce the penalty to zero if you get in contact within 12 months of the change to your income. Even after 12 months the penalty can be greatly reduced if you contact HMRC about the change before it’s discovered.

Example 1 – renting a property

Anna has inherited her mother’s house and rented it out. She’s retired and doesn’t normally need to complete a tax return. But she needs to check if the rent takes her income above her personal allowance for Income Tax. If it does, then she should contact HMRC and request a Self Assessment return to declare it.

Example 2 – selling a taxable asset

Thomas sold a second home in August this year at a profit, which is subject to Capital Gains Tax. He doesn’t normally need to complete a tax return, so Thomas should contact HMRC to request a Self Assessment return.


Example 3 – registering for VAT

Stephen runs a car body shop. His turnover for the past 12 months is about to exceed the £70,000 VAT registration limit. He needs to contact HMRC and register for VAT.

Example 4 – a hobby becomes a business

Jean works full time for a company, and pays her tax through the PAYE system. However, she also collects toys and has begun to buy and sell these on eBay, which provides her with a second income. Because this is treated as trading, Jean should register with us as self employed and complete a Self Assessment return.

Example 5 – the freelancer

Rashid is a photographer, employed by a company. However, he also takes wedding photographs at the weekend from which he makes a profit. Rashid should register with us as self employed and complete a Self Assessment return to declare this income.

Boxout: More information:

  • How to avoid a penalty  –
  • Self Assessment  –
  • Register with HMRC as self employed –
  • Check if your asset sale is liable for tax –
  • Register for VAT  –