Readers’ forum: Is there an alternative to using time apportionment?

My client purchased a house 20 years ago. He lived in the house as sole residence for 15 years and then moved out five years ago and rented the property out to a third party. Shortly after moving out he spend a considerable sum on capital improvements to the property. 

He is now in the process of selling the property and we are looking at the potential CGT liability. If you look at the value of the property at the date he moved out plus the cost of capital improvements there will be no real economic gain during the rental period. But if we look at the total gain over the period of ownership then – even taking account of the improvement costs – a considerable capital gain arises and on a time apportionment basis a quarter of this gain (roughly) will be exposed to tax.

My...