Rental Income and Cost of Finance Reduction Split With Spouse

I am looking to assign 60% of the rental income from a single property to my wife as beneficial holder. As it stands, the property has a mortgage under my name alone. However, my wife and I split the cost of the mortgage by way of paying equal amounts into a joint account out of which the payment to the lender is made on a monthly basis by direct debit. Would my spouse by able to claim the cost of finance relief against her share of the rental income simply by evidencing her contribution to our joint account? Or will HMRC only recognise her right to finance relief if she were named in the mortgage itself? In the latter case it would be evidenced by Tenancy in Common mortgage arrangement to account for the uneven split of 60/40.

Hi Armen,
Where a property is owned jointly by a husband and wife income, expenses are treated as being split on a 50/50 basis unless a declaration is made on Form 17.
That split should be on a percentage basis other than 50/50.
Such a declaration must be accompanied by evidence, such as a Deed of Trust, that the property is owned on that basis, please see following link for details of Form 17.
Declare beneficial interests in joint property and income
Thank you.