Double Entry System Bookkeeping and Accounting

Definitions, Meaning, and Transaction Examples

Most businesses use double entry accounting, a system in which every financial event causes two transactions, a debit in one account and an equal offsetting credit in another account.

When a company establishes an accounting system, it must 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, in which each financial event brings at least two changes in the accounts: A credit entry in one account along with an equal, offsettingdebit entry in another account.

The practice of using two account entries for every transaction in this way serves two purposes:

First, the double entry system provides a "built in" form of error-chceking. When the double entry system is used properly, the sum of all debit entries in the account ledgers for the accounting period must equal the sum of all credit entries. That is, at all times:

Total Debits = Total Credits

A mismatch in these two totals indicates that a bookkeeping error has been made. For more on error-checking, see the encyclopedia entry on trial balance.

Secondly, double entries maintain the balance in the so-called accounting equations: 

Assets = Liabilities + Owners Equity    

Debits = Credits

Keeping the company's accounts and maintaining the balance in these equations, in turn, means that the organization's balance sheet (statement of financial position) provides an accurate basis for assessing the company's financial structure, it's capital structure, and financial statement metrics (ratios).

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 its assets, liabilities, equities, revenues, and expenses. The accounting system also provides the basis for the 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 value and 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 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):

Grande Corporation Journal for Fiscal Year 20YY
Date	Account	Debit	Credit
30-Jun-20YY 30-Jun-20YY 31-Jul-20YY 31-Jul-20YY	630  Bad debt expense  120       Allowance for doubful accounts  770  Depreciation expense, factory manufacturing equip  175       Accumuulated depreciation expense, factory               manufacturing equipment	$137,000 $2,782,000	$137,000 $2,782,000

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.

Example Chart of Accounts

The example chart of accounts below is should be thourght of as an extract from a chart of accounts, rather than a complete chart. It shows the structure and general approach to account numbering and naming, but a complete example—even for a very small company—would no doubt list many more accounts.

Acct No	CHART OF ACCOUNTS
Asset Accounts - Current Assets
100	Petty cash
101	Cash on hand
103	Regular checking account
105	Payroll checking account
110	Accounts receivable
120	Allowance for doubtful accounts
130	Work in progress inventory
139	Finished goods inventory
140	Prepaid expenses
150	Employee advances
Asset Accounts - Fixed Assets
160	Furniture and fixtures
162	Vehicles
163	Factory manufacturing equipment
165	Buildings
169	Land
170	Accumulated depreciation, furniture, fixtures
172	Accumulated depreciation, vehicles
175	Accumulated depreciation, factory mfr equip.
179	Accumulated depreciation, buildings
Asset Accounts - Other Assets
190	Accumulated amortization
194	Notes receivable, non current
Liability Accounts - Current Liabilities
200	Accounts payable
234	Payroll payable
235	Accrued fees
240	Accrued interest
Liability Accounts - Long Term Liabilities
260	Bonds payable
270	Discount on bonds payable
280	Bank loans payable
290	Equipment payable
Equity Accounts
320	Owner capital
350	Retained earnings
380	Dividends
Revenue Accounts
410	Product sales revenues
420	Services sales
430	Rental property revenues
450	Interest earned revenues
Expense Accounts - Cost of Goods Sold
520	Raw materials costs
530	Direct labor costs
540	Indirect labor costs
550	Manufacturing plant costs
Expense Accounts - Other
601	Supplies expense
630	Bad debt expense
650	Advertising expense
720	Salary and wage expense
735	Travel expenses
750	Equipment lease expense
760	Depreciation expense, vehicles
770	Depreciation expense, factory mfr equipment
800	Other expenses