Books of original entry, also known as primary books or prime entry books, are the books where transactions are initially recorded before being transferred to the general ledger. These books are used in the double-entry bookkeeping system to maintain accurate and organized financial records. Some common books of original entry include:

1. Cash Book: This book records all cash transactions, including cash receipts and cash payments.

2. Sales Journal: It records all credit sales made by a business.

3. Purchases Journal: It records all credit purchases made by a business.

4. Sales Returns and Allowances Journal: It records all returns or allowances granted to customers for sales made on credit.

5. Purchases Returns and Allowances Journal: It records all returns or allowances received from suppliers for credit purchases.

6. General Journal: It records all non-routine or adjusting entries that cannot be recorded in other specialized journals.

7. Petty Cash Book: It records all small cash expenses made by a business.

These books of original entry serve as a chronological record of transactions and provide a detailed audit trail for financial analysis and reporting purposes.