Reasonable excuse for failure to notify high income child benefit charge liability

The taxpayer and his partner (Ms A) had a child in 2006. Ms A claimed child benefit for that child and also for her son whom she had with her previous partner. The taxpayer and Ms A lived together but kept their financial affairs separate – neither knew how much the other earned and the taxpayer did not know Ms A received child benefit. Since they were not high earners HMRC did not send them information about the new high income child benefit charge (HICBC) in 2013.

The taxpayer completed self assessment tax returns for the years 2012-13 to 2015-16 but was not a higher-rate taxpayer. In March 2017 HMRC decided to take him out of self assessment because he was employed and his income was dealt with under PAYE. However in 2016-17 and following years his income exceeded £50 000 making him liable to the HICBC.

In...