Partners and couples living together can split income from a jointly owned rental property in any ratio, meaning they can save £100s or £1,000s per annum if only one of them is a higher rate tax payer, by transferring up to 90% of the rental income to the one not working or on low income.
However, the same situation for a married couple, or those in a civil partnership, does not allow this. The rental income must always be split 50:50 if the property is jointly owned. This is totally unfair and discriminates against married couples, especially those where the mother has given up work to care for young children and really needs this income (and has lost child benefit, if her husband is a higher rate tax payer!).