Changing Beneficial Ownership to Wife on Property with Mortgage

I'm looking for some clarity. I own 3 properties. 1 has a mortgage, the other 2 don't. I'm looking to add my wife onto the properties as a beneficial owner, I will retain legal ownership. I would like to either have her as 100% benefactor, or split 90% to her, and keep 10%, I'm seeing a LOT of conflicting/confusing information around how to make my wife a beneficial owner. Some are saying it's just a form I can complete, others are saying it has to be done via a solicitor. I've seen multiple recommendations for a Deed of Assignment, Deed of Trust & Form 17 and I'm just confused as to what is actually needed. Some say I need to actually change the official property deeds too. Please can you CLEARLY advise, step by step, as I want to do this correctly. 1. What forms do I need to complete? 2. Where do I get them from? 3. Do I need to involve a solicitor?

Hi, 
This forum is for general queries only and we do not provide step by step guidance. Please refer to our Trusts, Settlements and Estates Manual:
TSEM9150 - Ownership and income tax
TSEM9170 - Ownership and income tax: legal background: ownership income follows property - variation
You can assign your wife as beneficial owner of the property using a deed of trust or deed of assignment as set out here:
TSEM9520 - Ownership and income tax: express trusts - written declaration
You will not be required to submit the declaration to us, but must keep a copy for your records as this may be requested at a later date.
A form 17 election is only required when the property is held jointly and there is an unequal split of beneficial interest. You may want to seek advice from a solicitor or for more specific queries our contact details are here:
Contact HM Revenue & Customs
Thank you.