HI THERE
I WISH TO SELL MY RENTAL PROPERTY ( my home prior to marriage )
AFTER TAKING INTO ACCOUNT PRIVATE RESIDENCE,LETTING ALLOWANCE ETC
I WILL BE EXPOSED TO C.G.TAX ON CIRCA £40k to £50k
IF I WERE TO TRANSFER FULL OWNERSHIP TO MY WIFE AND WE THEN RESIDED IN
THE PROPERTY AS OUR PRINCIPLE PLACE OF RESIDENCE WOULD MY WIFE BE
LIABLE FOR C.G.TAX UPON DISPOSAL AT A FUTURE DATE.
TO DATE MY WIFE HAS NEVER RESIDED IN OR RECEIVED ANY INCOME FROM THE PROPERTY.
REGARDS
PAUL

Not enough information.

You can nominate your old home as your principal private residence (PPR) by writing to HMRC, provided you lived in it at some stage, But you can only nominate one property. Have a look on HMRC's website for the detailed rules.

When you do sell, as you previously lived in the property, you will be deemed to also have lived in it for the last 18 months. Thus say you had owned the property for 12 years, living there 6, HMRC will treat you as having lived there for 7.5 years. This means any gain will be reduced by 7.5/12 before it is taxed.

Hope this helps. As it is only my view and not advice, you may want to look at HMRC's website or indeed take professional advice.