By default, an individual account’s start date is the start of the current financial year. You can visit the Account edit page from Chart of Account and change the account start date to any desired date in the past.

Also, Previous year data means the closing balances of the last financial year ending, balances are to be updated in the current financial year under the chart of accounts as opening balances, if the user has a credit opening balance of an account then just put a minus sign(-) in front of the amount and save it.