It depends on particular State Vat act ...that which form is to be filled for change in address...as in UPVAT act form XII needs to be filled in for any kind of change in registration , be it change of address or any other change, then If u have photocopy of forms available with you that u filled at the time of applying for registration ..that would do, and if u dont have that copy then a fresh filled form, that needs to be filled in at the time of applying for registration ( Form as applicable in that particular state vat act )has to be again filled and submitted, And proof of that new address, which generally include electricity bill and rent agreement or copy of registry of the new address have to be attached therewith.The above documents need to be submitted in the VAT department and after survey of that place, address gets changed.