It began in Britain in 1999, when separate tax favoured products for deposits and for shares were merged into one account, and it spread to Japan as NISA before Korea introduced its own version in 2016. Gains and losses inside the account are netted before tax, so the more products a saver keeps in one account the better it works. Contribution limits, minimum holding periods and the range of eligible assets differ by country, so the same name can mean very different benefits.