Those who fail to register for self-assessment tax returns could face a penalty of up to 100% of the tax due.
HMRC may also send out penalties if documents are sent in wrong or information is missed regarding tax liabilities.
Child Benefit changes
Child Benefit is worth £20.30 a week for your first child and £13.40 for any additional children until they turn 16, or 18 and are in full-time education.
However the Government has restricted the number of people that can claim Child Benefit - and exactly what they can claim - in order to cut costs. They've done that by charging a tax on the benefit, which you will need to declare in a self-assessment tax return, unless you opted out of receiving the benefit before 7th January this year.
The tax parents will need to pay back varies depending on their income. If one parent earns more than £60,000, the tax is equal to the full amount of Child Benefit. If they earn between £50,000 and £60,000 it works out at 1% for every £100 of pre-tax income they earn of more than £50,000.
Letters have already been sent out to parents who will be affected by the changes. If you're confused about how much you are entitled to, there is a tool on the HMRC website.
This deadline applies to anyone registering for self assessment, such as small businesses, people with untaxed property income, those with expenses of more than £2,500 and those with Capital Gains Tax to pay.
How to register for self assessment
To declare the Child Benefit you're receiving you'll need to fill in a self-assessment tax return. If it's your first time doing so, you'll need to register with HMRC online by completing the SA1 form before 5th October. You can also download a PDF version and post it or call HMRC on 0300 200 3310 and ask for it in another form, such as large print or Braille.
HMRC will then set up a tax record for you and create a Unique Taxpayer Reference (UTR). This is used to access the HMRC site through which you can send your online tax return before 31st January 2014. If you decide to send the return in by post the deadline is 31st October.
If you have already fill out a self-assessment tax return, you'll need to declare the Child Benefit you receive when you complete these forms.
You can find out more in our article How to get your online self-assessment tax return right.