Scotland was the first part of the UK to let 16-year-olds vote

For the 2014 independence referendum, the Scottish Parliament extended the vote to 16- and 17-year-olds, and an estimated three-quarters of them turned out. The Scottish Elections (Reduction of Voting Age) Act 2015 then made the change permanent for Scottish Parliament and council elections, first used in 2016. Wales followed for its Senedd in 2020.

— Scottish Parliament, Scottish Elections (Reduction of Voting Age) Act 2015 — asp 7, 2015