Please refer APVAT Rules 2005, see Rule 23 (6), it clearly says that you can file revised return in Form VAT 213 within six months from the original return filed. The rule says;---
"If any VAT dealer having furnished a return on Form VAT 200 finds any omission or incorrect information therein, other than as a result of an inspection or receipt of any other information or evidence by the authority prescribed, he shall submit an application on Form VAT 213 within a period of six months from the end of the relevant tax period. "
16 July 2010
After Revision, if VAT payable is still existing, then Interest @ 1% is calculated on balance VAT payable by the Department and Form 307 / 308 will be issued to the dealer for making interest payment and ensure that the revised return should be within six months from the original filing.