Just as HM Revenue & Customs has the right to repair an obvious error or mistake on a return, you also have the right to amend it within 12 months of the original filing date. If you have not detailed a source of income on the return, you are obligated to let HMRC know of the error.
The amendment may be in the form of a letter or you can submit an amended return showing the additional income in the correct box or supplementary page. If the error relates to a tax return which was filed more than 12 months ago, then you have to make an “Error and Mistake” claim by including the details in a letter. You cannot just send in an amended tax return.
You should advise HMRC as soon as you realise your mistake and try to pay the additional tax due as quickly as possible, as interest and surcharges will be due on the amount you have underpaid.
Interest will be applied on a daily basis at the rate in force at the time the tax was originally due, so if you missed the income off the 2008 tax return then you will have interest applied from 1 February 2009 until the day HMRC receive your payment. A surcharge of 5% will also be applied on the underpaid amount on 28th February 2009 and 31st August 2009.
By Jo Nockels
Disclaimer: Advice shared in this blog is intended to inform rather than advise. Taxpayer's circumstances do vary and if you feel that the information provided is beneficial it is important that you contact us before implementation. If you take, or do not take action as a result of reading this forum, before receiving our written endorsement, we will accept no responsibility for any financial loss incurred.