Exploring Various Subsidiary Books in Accounting

Picture a mid-sized trading company that buys and sells hundreds of items every single day. If every purchase, sale, cash receipt, and payment had to be written into one single journal, the page count would explode within weeks, and finding a single transaction later would feel like searching for a needle in a haystack. This is exactly the problem that subsidiary books solve. They split one overloaded journal into several smaller, purpose-built books, each dedicated to a specific type of transaction, so that recording stays fast, accurate, and easy to trace.

What subsidiary books actually are 🔗

A subsidiary book is a specialised record used to log transactions of a similar nature together, instead of cramming everything into a single general journal. They are also called day books or special journals, and they are still classified as books of original entry, meaning a transaction is recorded here for the first time, chronologically, before it is later posted to the ledger.

The logic behind this system is explained clearly in the study material published by the Institute of Chartered Accountants of India, which notes that the journal used for recording transactions may be further divided into several subsidiary books depending on the nature and size of the business. So instead of one journal doing all the work, a company sets up separate books for cash transactions, credit purchases, credit sales, returns, and bills, and each employee handling a particular book only needs to focus on that one category.

This division is not unique to India. In most accounting systems worldwide, everything other than the general journal is treated as a special journal, and AccountingTools describes these as journals used to record specific types of high-volume information that would otherwise clutter the general ledger, with totals transferred to the ledger periodically instead of transaction by transaction.

Why not just use one journal? 🔗

A single journal works fine for a small shop with a handful of transactions a week. But once volume grows, three problems appear. First, one journal becomes physically unmanageable. Second, one person cannot realistically journalise thousands of entries a month without errors creeping in. Third, tracing a specific transaction later becomes painfully slow when everything is mixed together in date order regardless of type. Subsidiary books solve all three by letting a business divide the work, assign different books to different staff, and retrieve any category of transaction quickly.

The cash book: the busiest subsidiary book of all 🔗

The cash book records every transaction involving cash and bank, both receipts and payments. It is the most frequently updated subsidiary book in almost any business because cash movements happen daily. Depending on how much detail a business needs, the cash book can take a few different forms.

Petty cash book and the imprest system 🔗

Large organisations also keep a separate petty cash book for small, everyday expenses like postage, stationery, and local conveyance, so the main cash book is not cluttered with tiny amounts. Most businesses run this on what is called the imprest system. Under this method, a fixed sum of money is handed to a petty cashier at the start of a period, and at the end of that period the cashier is reimbursed exactly the amount spent, bringing the float back to the original fixed figure. As AccountingCoach explains, this keeps the petty cash ledger account sitting at a constant balance, since only the reimbursement, drawn from the main bank account, moves through the books each time.

Purchases book and purchases returns book 🔗

The purchases book, sometimes called the purchases day book, records only credit purchases of goods that a business normally deals in or uses in production. A cash purchase never goes here; it goes into the cash book instead. Similarly, buying furniture or a delivery van on credit does not belong in the purchases book either, because that is not the kind of good the business trades in. Such an entry is instead recorded in the journal proper.

When goods bought on credit are later returned to the supplier, perhaps because they were damaged or did not match the order, that reversal is recorded in the purchases returns book, also called the returns outward book. Keeping this separate from the purchases book makes it much easier to see the net purchase figure and to track supplier disputes.

Sales book and sales returns book 🔗

The sales book mirrors the purchases book on the selling side. It records only credit sales of goods the business normally deals in. Cash sales go straight into the cash book, and the sale of an old asset like unused office equipment does not belong here since it is not part of regular trading stock.

When a customer returns goods bought on credit, the transaction is entered in the sales returns book, or returns inward book. Separating this from the sales book keeps gross sales and returns visible independently, which matters for calculating net sales accurately at the end of a period.

Bills receivable book and bills payable book 🔗

Businesses often settle credit transactions using bills of exchange or promissory notes rather than plain book credit. When a business receives such a bill from a customer, promising payment on a future date, it is recorded in the bills receivable book. When the business itself accepts a bill promising to pay a supplier later, that goes into the bills payable book. These two books let a business track exactly which bills are due for collection and which are due for payment, along with their maturity dates, without digging through the general ledger.

Journal proper: the book for everything else 🔗

After cash, credit purchases, credit sales, returns, and bills are all pulled into their own books, what remains for the journal proper are the transactions that do not fit any specialised category. This includes opening entries at the start of a new accounting year, closing and adjusting entries, entries to rectify earlier errors, and one-off transactions such as goods given away as charity or an asset purchased on credit. In many businesses, the journal proper actually sees far fewer entries than the other subsidiary books, but it remains essential for anything unusual.

Why this categorisation actually matters 🔗

Beyond keeping records tidy, subsidiary books deliver real operational benefits. Dividing entries into separate books lets a business assign different staff to different books, spreading the workload instead of relying on a single overworked clerk. Since each book handles only one type of entry, mistakes are easier to spot and correct, and each book effectively acts as its own audit trail during a review or external audit. AccountingTools points out that this structure also strengthens internal control, since assigning specific journals to specific employees reduces the risk of fraud while making it simpler to verify data later.

There is also a real efficiency gain at posting time. Instead of transferring every individual entry to the ledger one by one, a business can total each subsidiary book at the end of a period, usually monthly, and post that single summarised figure to the relevant ledger account. This alone can save enormous amounts of clerical time in a business processing thousands of transactions.

Subsidiary books in a GST and software-driven world 🔗

Manual subsidiary books written by hand in ledgers are now rare in mid-sized and large Indian businesses, since most run on accounting software that automatically sorts entries into the correct category the moment an invoice is created. But the underlying logic has not disappeared; it has simply moved into the software’s architecture. Sales and purchase registers, which are functionally the modern equivalents of the sales book and purchases book, are now a compliance requirement rather than just good practice. Under the GST framework, every registered business is legally required to maintain accurate accounts of outward and inward supplies along with related invoices, and the rules under the CGST Act specify that these records, including invoices, credit notes, debit notes, and delivery challans, must be preserved and made available on demand. In other words, the discipline of grouping similar transactions that subsidiary books introduced over a century ago now underpins a legal filing requirement, not just an accounting convenience.

This is also why understanding subsidiary books remains foundational even for students who will spend their careers working inside ERP systems rather than physical ledgers. Every software-generated report, be it a GSTR-1 sales summary or an accounts payable ageing report, is still built on the same basic idea of separating transactions by type before summarising them.

What do you think? If your college or a small business you know still keeps some manual registers alongside digital software, which subsidiary book do you think is hardest to fully automate, and why might a business choose to keep a manual check on it anyway?

References

1. https://resource.cdn.icai.org/74599bos60479-fnd-cp1-u1.pdf
2. https://www.accountingtools.com/articles/special-journals
3. https://www.accountingcoach.com/blog/imprest-petty-cash
4. https://taxinformation.cbic.gov.in/content/html/tax_repository/gst/rules/cgst_rules/active/chapter7/rule56_v1.00.html