• In case of large business organisation numerous transactions takes place with respect to purchase, sales, cash etc. Journalization of each of these transactions separately is laborious and time-consuming.
  To solve this problem subsidiary books are prepared.
• Subsidiary book  is  a  book  of   original entry  generally  maintained  by  large organisation  wherein  cash  and  cash transactions  are  directly  recorded avoiding cumbersome process of Journalization without sacrificing the fundamental principle of double entry book keeping system.

Normally, the following subsidiary books are used in business :-

• Cash book: To record cash, bank and discount transactions.
• Purchase book: To record transaction relating to credit  purchases of goods in trade.
• Sales book: To record transaction relating to credit sales.
• Purchase return book: To record transaction relating to purchase return.
• Sales return book: To record transaction relating to sales return.
• Bills receivable book: To record the receipts of the promissory notes or hundies.
• Bills payable book: To record the issue of the promissory notes or hundies.
• Journal proper: To record other transactions for which no specific book is maintained, and for recording entries to rectify mistakes in books of accounts.