Thousands of UK working families could be missing out on tax-free childcare worth up to £2,000 a year, according to HMRC.

Tax-Free Childcare – the 20 percent childcare top-up – provides eligible working families with up to £500 every three months (or £1,000 if their child is disabled) towards the cost of holiday clubs, before and after-school clubs, childminders and nurseries, and other accredited childcare schemes.

The scheme is available for children aged up to...