Introduction:
In accounting, a cash book is a financial ledger that records all cash transactions, including both cash inflows and outflows. It serves as a primary source document for recording cash transactions and plays a crucial role in maintaining accurate financial records.

Cash Book with Double Column:
A cash book with double columns is a specialized format of the cash book that includes two columns on each side - one for cash transactions and the other for bank transactions. This type of cash book is commonly used by businesses to record both cash and bank transactions simultaneously.

Reasons for Using Cash Book with Double Column:
1. Separation of Cash and Bank Transactions: The double column cash book allows for the separation of cash and bank transactions, making it easier to track and analyze the inflows and outflows of both types of funds.

2. Easy Reconciliation: By recording cash and bank transactions in separate columns, it becomes simpler to reconcile the cash book with bank statements. This reconciliation process helps to identify any discrepancies or errors in the recorded transactions.

3. Comprehensive Record-Keeping: A cash book with double columns provides a comprehensive record of all cash and bank transactions, enabling businesses to maintain accurate financial records. This record-keeping is essential for financial reporting, auditing, and decision-making purposes.

Example Scenario:
In the given scenario, the proprietor sold his personal assets worth Rs. 20,000/- for Rs. 17,000/- in cash, which was then deposited into the bank account of the business. Here's how this transaction would be recorded in a cash book with double columns:

Cash Column:
- Date: The date of the transaction.
- Particulars: A brief description of the transaction, such as "Sale of personal assets."
- Cash Receipts (Dr.): The amount received in cash, which is Rs. 17,000/-.
- Cash Payments (Cr.): Since there are no cash payments in this transaction, this column remains blank.

Bank Column:
- Date: The date of the transaction.
- Particulars: The same description as in the cash column.
- Bank Receipts (Dr.): The amount deposited into the bank account, which is Rs. 17,000/-.
- Bank Payments (Cr.): Since there are no bank payments in this transaction, this column remains blank.

Impact on Cash Book:
As a result of this transaction, the cash column will show an increase of Rs. 17,000/- in cash receipts, while the bank column will show an increase of Rs. 17,000/- in bank receipts. Therefore, the cash book will reflect a total increase of Rs. 17,000/- in both cash and bank balances.

Conclusion:
In conclusion, a cash book with double columns is a useful tool for businesses to record and track cash and bank transactions simultaneously. It allows for the separation of cash and bank transactions, simplifies the reconciliation process, and provides comprehensive record-keeping. By accurately recording the proprietor's sale of personal assets in the cash book with double columns, the business can maintain transparent financial records and effectively manage its cash and bank balances.