Hi Piotr,
Thank you for your question.
Where the joint owners are husband and wife or civil partners, profits and losses are treated as arising to them in equal shares, known as the 50/50 rule.
If both entitlement to the income and the property are in unequal shares, a form 17 election can be made to allow profits or losses to be split according to their actual share of ownership in the property.
You’ll also need to provide evidence that your beneficial interests in the property are unequal, for example a declaration or deed.
For further information, please see:
Declare beneficial interests in joint property and income
Thank you.