Q.Explain the meaning of Subsidiary Books. Why does a trader sub-divide the Journal into several such books instead of using a single Journal?

A business dealing in hundreds of transactions a day cannot realistically manage with just one Journal, and this question asks you to explain exactly why.

Subsidiary Books are books of original entry, other than the main Journal, each recording one specific, recurring class of transaction (e.g. the Purchase Book records only credit purchases of goods). A trader sub-divides the Journal because a single Journal for every transaction would be too long, would slow down and complicate ledger posting, and would give no single person clear responsibility over any one class of transaction.

Subsidiary Books are books of original/prime entry, other than the main Journal, each used to record one specific class of similar and recurring transactions — for example, the Purchase Book records only credit purchases of goods, the Sales Book only credit sales of goods, and so on. A transaction recorded in a subsidiary book is still recorded there for the FIRST time, exactly as the Journal would otherwise do; the only difference is that each book specialises in one kind of transaction.

A trader sub-divides the Journal into these several books, instead of relying on one common Journal, for the following reasons:

1. Division of labour — different staff members can be made responsible for different books, instead of one person handling every kind of entry.
2. Specialisation and efficiency — a clerk handling only one book (say, the Purchase Book) becomes quicker and more accurate at that specific job.
3. Saving of time — postings to the ledger can be made periodically from TOTALS of a subsidiary book (e.g. once a week/month) instead of transaction by transaction, cutting down the number of ledger postings sharply.
4. Easy checking and control — transactions of the same kind, grouped together, are far easier to cross-check (e.g. total credit purchases so far this month) than if scattered through one mixed Journal.
5. Prompt and complete information — the running total of a subsidiary book is available at any time without searching a large, mixed Journal.
6. Reduced errors and fraud — with different persons responsible for different books, and each book self-totalling, mistakes and irregularities are easier to detect.

Students sometimes describe Subsidiary Books as "types of ledgers" — they are NOT ledgers; they are books of ORIGINAL entry (the same stage as the Journal), and postings from them still go on to the ledger afterward, exactly as postings from an ordinary Journal would.