New HMRC figures indicate over 370,000 people have already opted out of Child Benefit since the High Income Child Benefit Charge was introduced on 7 January.
People who continued to receive Child Benefit payments for their family after January will be required to register for Self Assessment by 5 October 2013 in order to repay the benefit received between January and April 2013.
However, those who opt out before the 28 March deadline will not be required to file a tax return in future years.
Lin Homer, chief executive at HMRC, said: "Anyone wanting to opt out of Child Benefit payments can do so at any time. It is really easy – just go to our website.
"Anyone with an income over £60,000 who has received Child Benefit since January needs to register for Self Assessment by 5 October to repay some or all of this year’s benefit, but if they opt out now this will be a one-off."
For people with income of more than £60,000 the tax charge is the full amount of Child Benefit. Those earning between £50,000 and £60,000, the tax charge is gradually increased incrementally to 100 per cent of the Child Benefit.
Families should note that the decision to opt in or out of Child Benefit payments is far from final; people can opt back into the scheme at any time. However those earning over £50,000 who have received Child Benefit since 7 January 2013 will be required to register for Self Assessment and file a return for that period, regardless of whether they are now choosing to opt out.
For further information on the newly implemented High Income Child Benefit Charge visit our facts and information page to see how the changes affect you.