Disclosure of change in rate of depreciation

A company dealing in software development has changed the rate of depreciation on software developed by it over the years from WDV @ 40% to the useful life expectancy(in this case 15 yrs) of the developed software .How will this change in rate be disclosed in the financial statements and what all disclosure are required so as to give fair treatment in the books of accounts.

Please provide a sample of "Disclosure in notes to account to Balance sheet" for the same.

Kindly guide on this issue.

Thanks