No, its not mandatory to enter the opening balances. However, entering your balances from your previous accounting software or book of accounting is necessary to ensure continuity in your accounting.
If you’re switching to Zoho Books at the end of your financial year, all the closing balances of the previous year will be entered as your opening balances for the current year in Zoho Books. If you’re switching to Zoho Books at during any time of the financial year, you can generate a Trial Balance to identify all the debit and credit balances of your accounts.
and GST filing.