Capital gains effect

In the year 2014-2015 i entered into a sale agreement with the party with the condition that i will transfer the possession only when i receive the money. I get the money next year in 2015-2015 so i give my capital gains to tax in 2015-16 but the department holds that it should be taxable when i entered into the agreement. Now my query is , IS there any case law which holds true to the fact that it can be taxable in the year 2015-2016? i want the name of the case laws please help!! Thanks