If you are required to complete a self-assessment tax return, HMRC may charge penalties if you miss the deadline for making a filing or payment. 

There are also penalties if you fail to register on time for self-assessment. If you register late and do not pay your tax bill by the required deadline, you may receive a ‘failure to notify’ penalty. This is calculated based on the amount of tax still outstanding and is usually issued within 12 months of HMRC receiving your return.

If you submit your tax return after the deadline, you will typically receive an initial £100 penalty. This is followed by daily penalties of £10 per day after three months (up to £900), and further charges at six and twelve months based on a percentage of the tax due or a fixed amount, whichever is higher.

If you pay your tax late, additional penalties of 5% of the unpaid tax may be charged after 30 days, six months and twelve months. In addition, you will also be charged interest on the outstanding balance until it is paid.

Penalties must usually be paid within 30 days of the penalty notice date, and failure to do so may result in further enforcement action. If you believe a penalty has been issued incorrectly, you can appeal where you have a reasonable excuse, and HMRC will consider your circumstances before deciding whether to cancel or reduce penalties charged.