Vat returns

Dear Sir,

My client from Andhra Pradesh sold goods to one customer in Andhra Pradesh and raised Tax Invoice , My client files vat return and pay vat amount for particular invoice.

Now the Purchaser intends to returns goods

My question is whether my client is required to  give a credit note. if yes ? with Tax or without tax. because Vat amount is already paid to department.

 kindly suggest me