You have to file along with VAT/CST (200 & 200A) return, FORM 200B (annual return) with the Assessing Authority.
Please log on to www.apcommercialtaxes.gov.in and go to APVAT Forms link and download Form VAT 200B and fill the details on annual basis and file accordingly. There is no assessment concept in VAT Regime. Filing of return itself is the self assessment (monthly assessment) Assessment concept is still existing under CST Act as there is liability and forms to be collected.
Hope ur doubt is cleared. The due date for annual return will be announced by Dept itself. Mostly it will be 7th of April 2010. Please check it out for the date in department website.