02 April 2010
Please check the VAT amendment date as per the state notification.
If the amendment is wef 01-04-2010 and your purchase order is on 30-03-2010 then the old rate will be applicable and if the PO date is later than or on 01-04-2010 then new rate will be applicable. This is applicable for the sales too.
Hope it is clear for you. If any clarifications, plz let us know.