Income Tax Depreciation

Hello SAP Guru,s

Can anyone tell me how the Income Tax Dep works in SAP.

I have created Group Assets and Dep Keys accordingly and we made lot of acquisitons during this year with out opening WDV for Group Assets.But while I run the In come Tax Dep Report through J1IQ it is showing as report date 31.12.2007 and my current date is 20.07.2007.But after executing I didnt any Tax depreciation and it is coming as blank.

Can any one explain why it is occrring like this ?

Is there any additional customization I have to be made for this ?

What is the steps I have to follow to run Income Tax Depreciation as per Indian Income Tax Act ?

It would be a great help I will be give fill credit.

Thanx