Hi. I have a different answer.
It's not clear whether the property was ever used for a business other than just letting which the Treasury does not see as a business in the true sense of the word. A gain made on the sale of a property which is sold and which was only ever let during your ownership of it will not qualify for ER.
Even if there was a business at some point, from the time that the property was let or 6 April 2008 if earlier until its sale,that part of any gain will not qualify for ER. Take a look at Example 4 in HS275 here:
I hope this helps but let me know if you have any further questions.
From begining, the property was used as a Physiotheraphy Clinic for 3 years and then the premises was too small to expand. The Clinic then moved to a much larger premises, rented. Once moved out, the property was leased out to a company, which is still there.
Does this means that for initial 3 years of business, the gain value of the property would be at ER rate??
What period did the clinic cover exactly? When did the letting start?