You have been able to pool your tax allowance for 10 years.
In 2000, the Married Couple's Allowance was scrapped, and non-employed parents were stripped of their right to a tax-free allowance. Today, if both parents go out to work and put their children into childcare, the government gives them each a £6,035 tax-free allowance, as well as heavily subsidising their child care costs. But if they prefer to look after their children themselves, sacrificing one income and foregoing all the child care subsidies, the government penalises them by making the stay-at-home parent forfeit her (or his) right to a tax-free income.