If you own a property jointly with your wife or Civil Partner, then a declaration can be made via Form 17 to split the beneficial share of a property. This means that any share of the rental income earned on the property or capital gains resultant on the sale of the property, can be split into shares other than 50/50 between the both of you (e.g. 80/20). No split other than 50/50 can be accepted until a declaration is required.
This is very helpful if one of you is a higher rate tax payer and the
other a lower rate tax payer, as it will allow you to attribute a higher
percentage of rental income or Capital Gain to the lower rate tax payer
and therefore pay more income tax at 20% rather than at 40% or Capital
Gains Tax at 18% compared to 28%.
The form has to be signed and dated by both spouses or civil partners,
but can then be sent to the tax office of either spouse or civil
Once a declaration is made it remains in force until the couple's
interests in the property or income change, or they stop living together
as a married couple or as civil partners of each other.
A copy of Form 17 can be downloaded from HMRC’s website.