Subsidiary books.
Section 335
SEC. 335. Subsidiary books. — All corporations, companies, partnerships, or persons keeping the books of accounts mentioned in the preceding section may, at their option, keep such subsidiary books as the needs of their service may require: Provided, That where such subsidiaries are kept, they shall form part of the accounting system of the taxpayer and shall be subject to the same rules and regulations as to their keeping, translation, production, and inspection as are applicable to the journal and the ledger.