Mortgage interest on buy to let

My daughter and her husband have a joint mortgage on what was their PPR but is now let. They are proposing to submit Form 17 for the right to rental income to be allocated 100% to my daughter. The mortgage will continue in joint names. Will my daughter be able to claim relief for 100% of the mortgage interest against her 100% of the rental income or only 50% as the mortgage is in joint names. Thank you

Hi BOBC,
As your Daughter pays a portion of the mortgage, she would still be able to claim her 50% share, however, rental income would be 100% submitted by her Spouse from the date the Form 17 has been completed. 
Thank you. 
 

Thank you for the reply

My daughter and her husband own the property as joint tenants. Would the following be sufficient as a declaration of trust to transfer the income to my daughter? would this declaration need to be submitted to HMRC with the Form 17? Thank you nfor your continuing help

Hi BOBC,  
Form 17 can only be used by a married couple or civil partners.
Please see this guidance:
TSEM9844 - Property held jointly by married couples or civil partners: Form 17 rule: Who can make a declaration?
The property will have to be taxed on the same proportion that they own the property.
Further information for non-married couple can be found at:
TSEM9200 - Ownership and income tax: legal background: joint ownership - contents
Thank you. 

They ara married. Daughter and her husband 

Hi BOBC,
Thanks for your question.  A Form 17 election cannot be made if you the couple own the property as joint tenants.  Your property income cannot be split other than in equal shares.
Thank you.