The purpose of accounting is to provide information that can be useful for economic decision-making. For this purpose， we should have certain accounting principles that provide guidelines and a common ground to practice accounting and to communicate accounting information effectively. The most important principles are as follows： -Accrual -Historical cost -Realization -Matching -Conservation -Objectivity -Full-Disclosure -Consistency -Materiality The Accrual Principle The accrual principle holds that profit （or loss） is the difference between revenues and expensed for a period. It is not the difference between the cash receipts and cash payment for the same period. This principle complements the realization and the matching principles. According to it， the process of determining profit （or loss） is based on the accrual basis that is quite different from the cash basis.The accrual basis recognizes the impact of transactions on the financial statements in time periods when revenues and expenses occur. That is， revenues are recorded as they are earned and expenses are recorded as they are incurred. In contrast， the cash basis recognizes the impact of transactions on the financial statements only when cash is received of disbursed.
The historical cost principle Since one important function of the accountant is measurement， there must be a common basis that is meaningful to all interested parties. The most commonly used basis is historical cost， which means that most assets are recorded at their acquisition cost measured in terms of money paid. The exchange price between independent parties establishes the historical cost that is the basis for accounting. For example， assume that a building was purchased in 1983 for ten million dollars. This amount， the market value at the time of the purchase， is the basis fro recording the event in the accounting records. Subsequent to that purchase， the market price of the building may change as economic conditions change， but the objective fact of the purchase at the million dollars remains the same. Hence the use of historical cost is seen as ensuring greater objectivity in financial reporting than the use of figures based on estimates of current value， because it is factual and verifiable. The realization principle The realization principle indicates when revenues should be recognized. According to this principle revenues are normally recognized when the earning process is virtually completed-the goods pass （or service is rendered） to， and are （or is） accepted by， the customer. There are many revenue transactions such as installment sales and long-term construction contracts that pose revenue recognition problems.The principle requires that the accrual basis rather than the cash basis to be used for revenues. For example， completed transactions for the sale of goods on credit are usually recognized as revenue in the period in which the sale occurs， rather than in the period in which the cash is eventually collected.
The Matching Principle The matching principle defines when an expense should be recognized. It requires that in any period when！ revenue is recognized， the expense incurred in generating that revenue should be recognized. In other words， the expenses should be matched to and charged against the revenues in the same accounting period as the revenues are recognized. Some expenses reflect a direct cause-and-effect relationship where revenue and expense occur simultaneously. These expenses are usually called direct expenses which can be related directly and specifically to a particular revenue. Examples are cost of goods sold， sales commission expense， and delivery expense， etc.， but， in practice， quite a lot of expenses cannot be matched to particular revenue in that direct way. Examples are depreciation， shop rent， etc.， which is usually referred to as indirect expenses. In such case， the matching is done on a time basis. That is to say that the expenses for the period are related to the period rather than to specific revenues. The Conservation Principle （the prudence Principle） According to the conservatism principle， the accountant will take risk into consideration by recognizing both expenses and liabilities when there is some reasonable probability of some adverse event occurring. On expensesYand liabilitiesQwhen there is some reasonable probability8of some adverse eventAoccurring. On the other hand， the accountant will recognize revenues and assets only when there is virtual certainty of an advantageous event occurring. More specifically it means that suspected but uncertain losses should be anticipated. This principle is a prudent reaction to uncertainty and is adopted in order to ensure that adequate consideration is given to all inherent business risks.
The Objectivity Principle According to the objectivity principle， the accounting records from which the periodic accountingstatements are prepared must have objectivity and verifiability； they must be maintained in such a way that the individual bias or personal opinion of the accountant does not influence the accounting process， so as to ensure greater truth and reliability in accounting statements. The market values of some items， such as real estate， are constantly changing， and estimates of these values are matter of personal opinion or professional judgment， but they are not factual and objective. Historical cost， on the other hand， supported by business document such as sales slips， purchase invoices， is factual， objective， and verifiable. This gives reasonable assurance that any accountant viewing the evidence is likely to treat that financialLevent in the same way. Business documents provides the basic source of accounting records， and act as a basis for objectivity of the information.