Thank you for your reply...
Your period of ownership begins on the date you first acquired the dwelling house and it ends when you dispose of it. The final 18 months of your period of ownership always qualify for relief, regardless of how you use the property in that time, as long as the dwelling house has been your only or main residence at some point.
This is covered on Pages 3 and 4 of HS283 that I referred to in my last posting.
Bought property in Jan 2006
Moved out of property Dec 2011
Rented for period Jan 2012 to Jun 2015
Sold property end Jun 2015
Period as main residence - Jan 2006 to Dec 2011 = 72 months
Period rented – Jan 2012 to Jun 2015 = 42 months
Period of ownership – Jan 2006 to Jun 2015 = 114 months
Private residence relief plus additional relief
(72+18) = 90 months out of 114 month
Gain remaining after private residence relief
24 months out of 114 months
Lets say the gain is £114,000
Private residence relief (90/114) x 114,000 = £90,000
Gain subject to capital gains tax
(114,000-90,000) = £24,000
Letting relief available = £24,000
Net chargeable after letting relief = NIL
I hope this is helpful.