I am selling my house which I rent out and likely to make a

Hi.Can you tell me what the history of the house is please. Have it ever been your main home? If so, when did you buy it, move in, move out and let it (months and years please). Are you married? Is the house jointly owned and, if so, has it always been so?

Hi again.
Based on the information provided, you won't have any CGT to pay.
If you sell the property in December 2015 and make a gain of £40,000, £20,000 for each of you and your wife, by that time you will have owned it for 128 months of which it was occupied by you for 75, let for 47 and vacant for 6. The following figures apply to each of you:
The gain for the period the property was your main home will be exempt from CGT as will the gain for the last 18 months of ownership. That accounts for £14,531 (£20,000 / 128 months x 93 months). The remaining gain of £5,469 is that part of the letting period gain which is not covered by the last 18 months of ownership (20,000 / 128 x 35).
As the property was both your main home and it was let you are entitled to letting relief which is the lesser of:
1 £40,000,
2 the sum of the main residence period gain and the gain for the last 18 months of ownership of the property which is £14,531 and
3 the letting period gain of £5,469.
Letting relief of £5,469 will reduce the remaining gain of £5,469 to £0 so you should have no CGT to pay.
Take a look at HS283 here for more information on the main residence and CGT:
https://www.gov.uk/government/publications/private-residence-relief-hs283-self-assessment-helpsheet/hs283-private-residence-relief
I hope this helps but let me know if you have any further questions.