Company income tax record, voucher, bills

As per section 153, assessment under section 147 shall be made within a period of one year from the end of the financial year in which notice under section 148​ was served on the taxpayer. Notice under section 148 can be issued within a period of 4 (*) years from the end of the relevant assessment year.​ (*)

If the escaped income is Rs. 1,00,000 or more and certain other conditions are satisfied, then notice can be issued upto 6 years from the end of the relevant assessment year. In case, the escaped income relates to any asset (including financial interest in any entity) located outside India, notice can be issued upto 16 years from the end of the relevant assessment year.​

So If You Have Asset outside India Then Better To Maintain Last 16 Years Record And If Not Than For Atleast 8 Years