The ingredients of Section 18 of the Prevention of Corruption Act, 1988 are:

1) That the CBI may inspect the Accounts of the public servants and any bankers' books in so far as they relate to the accounts of the persons suspected.

2) They may also inspect the Accounts of other persons suspected to be holding money on behalf of the public servant.

3) They may take certified copies of the relevant entries therefrom.

4) it is mandatory that the bank would assist the police officer (defined under Section 17 and also specifically described under Section 18 of the Prevention of Corruption Act, 1988).

5) The term referred to above is not restricted to only one bank but all the banks where the accused person may be suspected of keeping his accounts or of any other persons suspected to be holding money on behalf of the public servants (including outsiders involved with him in the particular case). It is the reason that the cm is raiding at all the places simultaneously.

6) Section 18 does not speak anything about the lockers of the Bank court of the documents / papers provided to the CBI officers. They are generally summoned in the Court to substantiate evidence alongwith bank books of accounts.

The necessity to inspect arises when the cm has to investigate the case of disproportionate assets of the public servant under Section 13(1) (e) of the Prevention of Corruption Act, 1988. The CBI then looks for the assets, (movable and immovable property), cash and valuables held by him or any other persons, relatives and friends on his behalf called 'Benami Transactions': or "Benami Property" .
The Benami Transactions (Prohibition) Act, 1988 (45 of 1988) came into force 5th September, 1988 alongwith the Prevention of Corruption Act, 1988 (49 of 1988) which was passed by the Parliament on 9th September, 1988. The dates would give an idea as to how these two Acts have been closely associated with each other. Benami Transactions (Prohibition) Act, 1988 is an Act to prohibit benami transactions and the right to recover property held benami for matters connected therewith or incidental thereto. Section 2 of the Benami Transactions (Prohibition) Act defines what are the benami transactions prescribed under the Act and what does the property means. Section 3 provides for the prohibition of benami transactions. Section 2 and 3 of the Benami Transactions (Prohibition) Act, 1988 are reproduced hereunder:

Section 2. Definitions. -In this Act, unless the context otherwise requires,-
(a) "Benami transaction" means any transaction in which property is transferred to one person for a consideration paid or provided by another person;
(b) "Prescribed" means prescribed by rules made under this Act;
(c) "Property" means property of any kind, whether movable or immovable, tangible or intangible, and includes any right or interest in such property.

Section 3. Prohibition of benami transactions.-
(1) No person shall enter into any benami transaction.

(2) Nothing in subsection (1) shall apply to the purchase of property by any person in the name of his wife or unmarried daughter and it shall be presumed, unless the contrary is proved, that the said property had been purchased for the benefit of the wife or the unmarried daughter.

(3) Whoever enters into any benami transaction shall be punishable with imprisonment for a term, which may extend to three years or with fine or with both.

(4) Notwithstanding anything contained in the Code of Criminal Procedure, 1973 (2 of 1974), an offence under this section shall be non-cognizable and bailable.