Assesment

option to itr for the year before ( AY 2018-2019) is not existed now

If you will get a notice regarding then you  can file return  

If you are asking about vat assessment then the required documents will include
sales details
purchase details
stock transfer in detail
stock transfer out detail
monthly/quarterly return filed
tax payment details
trading account for the business
Audited balance sheet
Gross turnover details
any other documents as required by assessing officer