Practise of issuing debit & credit notes

I don't know what is mentioned under KVAT act but i have done Audit of HP & as per HPVAT act in case of any return of goods as u already know that the output tax will proportionately reduced & the reduction can only be done if the return of goods has been made within 6 months of selling that goods 

In case goods returned after 6 months from the date of sale then the seller have to pay output tax on whole sale made without any deduction of sales return & now is your answer that seller should issue a credit note & purchase will issue debit note consequently & yes it is in usual practice.