Unknown Bank Account

At the Year end 2019-20 in the month of February 20 current bank account was opened but no transaction were made through that bank account. A balance sheet was prepared by CA without adding the new bank account in it. In next financial year 2020-21 many creditors were paid by a from that bank account and payment were received in that bank Account with its operating balance Rs.12,000. How to add such bank account in in books of account without disturbing the balance of balance sheet.