34. An officer of Customs, not below the rank of Assistant Commissioner of Customs may, in the case of any mercantile firm or public body, if he so thinks fit, instead of requiring payment of customs-duties or charges as and when they become due, keep with such firm or body an account-current of such duties and charges, which account shall be settled at intervals of not exceeding one month, and such firm or body shall make a deposit or furnish a security sufficient in the opinion of that officer to cover the amount which may at any time be payable by it in respect of such duties or charges.