Double Entry System Bookkeeping and Accounting
Encyclopedia of Business Terms and Methods, ISBN 978-1-929500-10-9. Revised 2012-12-03.
When establishing an accounting system, entities choose to use either a single entry system or a double entry system. In business, the overwhelming majority of companies choose the double entry approach, by which each financial event brings at least two changes in the accounts: A credit entry in one account causes an equal, offsetting debit entry in another account.
The practice of using two account entries for every transaction in this way serves two purposes:
- Double entries play an error-checking role. The sum of all debit entries in the account ledgers must equal the sum of all credit entries. A mismatch in these two totals indicatesthat a bookkeeping error has been made.
- Double entries serve to maintain the "balance" in the so-called accounting equations:
Assets = Liabilities + Owners Equity and Debits = Credits
Keeping the company's accounts and maintaining the balance in these equations, in turn, means that the organization's balance sheet—or, statement of financial position—provides an accurate basis for assessing the company's financial situation.
The account as the fundamental building block of an accounting system
In business, each profit making company establishes an accounting system in order to manage and keep track of incoming and outgoing funds. The accounting system also provides the basis the basis for financial reports the company must file periodically.
The basic building block in such a system is the account, which can be defined as a place for recording changes in value (additions and subtractions) for one specific purpose. In fact, "specific purposes" are divided into five categories, and these categories represent the five—the only five—kinds of accounts possible in an accounting system:
First, there are the so-called "balance sheet" kinds of accounts:
1. Asset accounts: Things of value that are owned and used by the business.
Example: Cash on hand
Example: Accounts receivable
2. Liability accounts: Debts that are owed by the business.
Example: Accounts payable
Example: Salaries payable
3. Equity accounts: The owner's claim to business assets.
Example: Owner capital
Example: Retained earnings
Secondly, there are the so-called "income statement" kinds of accounts"
4. Revenue accounts: The amounts earned from the sale of goods and services.
Example: Product sales revenues
Example: Interest earned revenues
5. Expense accounts: Costs incurred in the course of business.
Example: Direct labor costs
Example: Advertising expenses
In reality, even a very small business may identify a hundred or more such accounts for its accounting system, and a very large company may identify many thousands. Nevertheless, for bookkeeping and accounting purposes, all named accounts fall into one of the five categories above (see Chart of accounts, below).
Every financial transaction for the company is recorded as a change in an account. If the company uses double-entry book keeping (as nearly all companies do), every financial transaction causes two equal and offsetting account changes, the change in one account called a debit and the change in another account called a credit.
In the double entry system, just how the bookkeeper and account handle each transaction for an account depends on which of the five account categories the account belongs to. Whether a debit or a credit increases or decreases the account balance depends on the kind of account involved:
|Debit (DR) Entry ...||Credit (CR) Entry ...|
|Asset account||Increases (adds to) account balance||Decreases (subtracts from) account balance|
|Liability account||Decreases (subtracts from) account balance||Increases (adds to) account balance|
|Equity account||Decreases (subtracts from) account balance||Increases (adds to) account balance|
|Revenue account||Decreases (subtracts from) account balance||Increases (adds to) account balance|
|Expense account||Increases (adds to) account balance||Decreases (subtracts from) account balance|
Suppose, for example, that a company acquires assets valued at $100,000. An asset account will increase (be debited) $100,000 (perhaps asset Account 163 from the chart of accounts below, Factory manufacturing equipment). The increase in account balance is called a debit because this is an asset account. However, the balance sheet is now temporarily out of balance until there is an offsetting credit of $100,000 to another account, somewhere in the accounting system. This could be, for instance:
- A credit of $100,000 to another asset account, reducing that account value by $100,000 (from the chart of accounts below, that could be a credit to asset Account 101, Cash on hand).
- If the asset purchase is financed with a bank loan instead of the company's cash, however, the offsetting transaction could be a credit to a liability account, increasing that account value by $100,000 (which could be Account 171, Bank loans payable).
In this way, the basic accounting equation always holds and the balance sheet stays balanced:
Assets = Liabilities + Equities
And, for every pair of account entries that follow from a single transaction:
Debits = Credits
See the encyclopedia Double entry system for more on the accounting mathematics involved in double entry bookkeeping.
Contra accounts (Valuation allowance accounts)
Not all accounts work additively with each other on the primary financial accounting reports—especially on the income statement and balance sheet. There are many instances where one account works to offset the impact of another account. The so-called contra accounts "work against" other accounts in this way. In some situations, the contra accounts reverse the debit and credit rules from the table above.
Contra-asset and contra-liability accounts are also called valuation allowance accounts, because they work to adjust the book value, or carrying value for assets or liabilities, as shown in the examples below.
The balance sheet example running throughout this encyclopedia has several contra account examples, including these under Assets:
You may notice from the chart of accounts example below, that Accounts receivable (Account 110 from the chart) and Allowance for doubtful accounts (Account 120) are both asset accounts. Allowance for doubtful accounts, however, is a contra asset account that reduces the impact (carrying value) contributed by Accounts receivable. The balance sheet result is a "Net accounts receivable" less than the Accounts receivable value.
In the same way, Account 163, Factory Manufacturing equipment carries the value of these assets at historical cost—what was actually paid for these assets. This will not decrease as long as the company owns the assets. However, the asset's book value does change downward from year to year, as shown on the balance sheet. Contra Account 175, Accumulated depreciation, factory manufacturing equipment, is subtracted from the Account 163 value, to produce the balance sheet result Net factory manufacturing equipment.
In each case above, incidentally there is also an expense category account involved, and those appear on the income statement, not the balance sheet. In the first example, the expense account is Bad debt expense and in the second case, the expense account is Depreciation expense, factory machinery. The offsetting debit and credit transactions might look like this way in the bookkeeper's journal (the chronological record of transactions):
Journal for Fiscal Year 20YY
630 Bad debt expense
770 Depreciation expense, factory manufacturing equip
All four transactions add to the value of the accounts listed. Debiting each of the two expense accounts adds to account value, as you would expect from the table in the previous section. However notice here that crediting the two asset accounts adds to their value as well—just the opposite of what the same table prescribes for asset accounts. For contra accounts in this situation the rules are reversed, so that the fundamental equation Debits = Credits still holds for every pair of transactions. The examples also show why a contra asset account is said to hold a credit balance.
The above examples show contra-asset accounts, but there are also examples of contra-liability accounts that operate in the same way. For example, on the liabilities side of the balance sheet, a long term liability account Bonds payable may be accompanied by another liability account, a contra liability account called Discounts on bonds payable. The value in the contra account reduces the company's actual liability from the stated figure in the Bonds payable account.
Contra liability accounts—like their contra asset account counterparts—also reverse the debit/credit "rules" from the table in the previous section. An addition to a liability account is normally a credit, but to a contra liability account, an addition is a debit. For this reason, contra liability accounts are said to carry a debit balance.