In tally ERP 9, how to restrict a user to make new entry in back date or alter the entry of previous date?

From Tally home/main screen (after opening a company)

Press Click on Company Info at right side of the screen, or press ALT+F3

Click on SECURITY CONTROL or press E

Choose TYPES OF SECURITY or press T

Hit ENTER key on Data Entry

you can enter number of days in DAYS ALLOWED FOR BACK DATED VOUCHERS