Countries differ, too, in how they treat the income of married couples. Some countries operate a regime of joint taxation, in which the incomes of a married couple are combined and taxed together, as a single unit. The UK used to do this—indeed the UK tax system used to treat the income of a married woman as the property of her husband until comparatively recently. In 1990 the UK switched to a system of independent taxation, in which the income tax is applied on an individual basis, and married couples pay the same tax as they would if they were two single individuals.