Rental income - apportionment with non married partner

I own a buy to let property purchased before meeting my current partner - property has a mortgage on it - (we live in a separate residential property) my partner and I are not married or in a civil partnership. I am a higher rate tax payer - she is lower rate. I would like to know whether there are any actions i can take to transfer either 50/50 split of rental income to her - or a different % split?. I have searched previous posts and can see deeds of trust etc but all seem to relate to people who are married - not non married co habiting partners.

Hi,
Thank you for your question.
A Declaration of Trust is a legally binding document that creates a trust. Most types of trust giving an interest in property to somebody who is not the legal owner now need to be registered with HMRC via the Trust Registration Service.
You can find guidance on the registration requirements and how to register here:
Register a trust as a trustee
There is also more information about what types of trust need to be registered at Trust Registration Service Manual - Types of trust that need to be registered: contents: excluded express trusts: contents: property ownership - HMRC internal manual - GOV.UK (www.gov.uk). 
Thank you.

Thankyou - by entering into a declaration of trust with my partner would that involve any stamp duty/capital gains tax etc etc considerations - or is it a simple transaction with no knock on impacts anywhere?

Hi
Unfortunately, we are unable to provide specific advice tailored to individual circumstances on this forum. This forum is for general queries only and is intended to help you self-serve. 
However following on from your previous question when entering a declaration of trust, this would essentially transfer a certain percentage of beneficial interests in the property, i.e. rental income and any expenses, without transferring legal ownership to the other party. 
There would be no stamp duty/capital gains applied. 
A Deed of Trust on the other hand, transfers the legal title to a third party, so any Stamp Duty/Capital Gains may apply. 
Customers with more complex enquiries like this often engage the services of a professional advisor or accountant and this may be something you wish to consider.
Thank you