Nearly half the couples eligible to claim marriage tax allowance are still failing to do so, according to HM Revenue and Customs (HMRC). The tax allowance - worth £230 a year - can be claimed by married couples or those in a civil partnership if they meet certain conditions. However, since it was introduced in 2015, only 2.2 million couples have claimed it, from 4.4 million eligible. The government said it had now simplified the application process. Last year, HMRC reported t