Adjustment of Inter state sales Return in monthly Vat Return

Dear sir,

in the month of Feb 2010 we have sold some material as inter state sales and accordingly filled my monthly Vat Returns.

But in the next financial year i.e in the month of april 2010 buyer returned the goods through challan.

so any one can tell me how the ( sales return) be adjusted in which tax period i.e Feb 2010 , March 2010 or April 2010.

in other words should i revised my feb month return or i can directly adjust it in april month.

Vishnu

Manager accounts