Section 215 of Companies Act, 1956 mention about Authentication of Balance Sheet and Profit and Loss Account
As per Section 215 (1) Save as provided by sub-section (2), every balance-sheet and every profit and loss account of a company shall be signed on behalf of the Board of directors by manager or secretary, if any, and by not less than two directors of the company one of whom shall be a managing director where there is one.
It does not say whether a Company is private or public according to this section every balance sheet and profit and loss account is required to be signed :
1) By Manager or Secretary and
2) Two Directors (one by MD if there is one)
If a Company is having both Manager and Secretary any one of them can sign the balance sheet and profit and loss account. If manager sign the B/s n P/l account it is not mandatory for CS to sign it.
In case no Manager is appointed in a Company then it is Mandatory for Company Secretary to sign B/S and P/L Accounts.
Signing of Balance Sheet and Profit and Loss Account has nothing to do with whether a Company is public or Private. It is required to be signed by Company Secretary.