While a balance sheet is a stock-based static statement that presents a company‘s financial position at a point in time, an income statement is a flow-based dynamic statement that describes a company‘s operating performance over a period of time. The period covered by an income statement must be clearly specified. The phrase "Income Statement of 30 June 1997" is meaningless unless it is intended to show the revenues and expenses for the single day 30 June 1997.
Historically, the income statement used to be a supportingstatement to the balance sheet. Without the income statement, we would record revenue as an increase, and expense as a decrease, of the equity account Retained Earnings. Such transactions are numerous. To simplify the bookkeeping, as well as to provide more useful information, the income statement was born.
Depending on how revenues and expenses are presented, there are roughly two formats of the income statement, the traditional multi-step format and the relatively new two-step format. The former has a few steps: Sales - cosplayt of Goods Sold = Gross Profit; Gross Profit - Operating Expenses = Operating Income; Operating Income ± Non-Operating Items = EBT ; EBT - Income Tax = Net Income.
Of course whether an item is operating or not depends on the nature of the business. For instance, while Interest Expense may be a non-operating expense for many companies, it is the most important operating expense for banks.
When a company has losses rather than earnings, it does not have to pay income tax. It may also be allowed to carrythe loss backward and/or forward, depending on the tax environment the company is in.
Different users of financial statements often have different needs. The multi-step format of the income statement is unlikely to suit all needs. Some American
companies took the lead to use the two-step format. In thisformat, the income statement contains basically two parts. The first part lists all sources of revenues while the second lists all kinds of expenses. A reader can prepare the income statement in any form to suit his purpose.
It must be pointed out that the net income shown in the income statement is an accounting profit, not cash flow. Inthe computation of accounting profit, cash receipts from selling farecards are not recognised as revenue. Rather, they are "Unearned Revenue" classified under Current Liabilities. Revenue is considered realised only after the bus service is provided and consumed. Similarly, insurance premium paid for any part of the next financial year will not go to the expense in the income statement. Rather, it will appear as Prepaid Expense, an item under Current Assets.
In accounting terminology, the income statement is prepared using the "accrual basis", not the outdated "cash basis". When China in 1994 proclaimed the adoption of the Western accounting system, the switch from the cash basis tothe accrual basis was the heart of the change.
中文 损益表资产负债表是个“静态”的报表，描述公司在特定时刻的财务情况。相对地，损益表是一个“动态”的报表，它陈述了某公司在“特定时段”的经营成就，即各项收入与本钱及其所产生的价值。因此“某年底损益表”或“某月底损益表”是没意义的，应该说是“某年度损益表”或“某月份损益表”。
就会计的进步历史而言，损益表可以说是资产负债表的一个附表，假如没损益表的话，大家就得把收入记为股东权益中“保留盈余”的增加，把本钱或成本记为保留盈余的降低。因为涉及收入与成本的买卖数目甚多，这种做法会导致簿记的烦乱混杂。为了简化簿记工作，也为了将各种收入支出分类，以提供更有用的管理资讯，损益表就应运而生了。
损益表依据它表列各项收入与成本的顺序，也有不一样的格式。传统的格式可称为“逐步式”，大致包含以下几步：第一步是从销货收入减去销货本钱（即卖出去的货品的拿货本钱），得到销货毛利。第二步是从销货毛利扣除各项营业成本（如运费、广告费等销售成本、薪金、水电等管理成本），得到营业损益。第三步是非营业项目；营业与非营业项目的区别因公司业务性质而异，比如利息收入是很多企业的非营业收入，但肯定是银行业的营业收入。营业损益加（减）非营业收益（损失）后得到的是税前盈利或损失。税前盈利减去所得税后就是税后净利。公司如有税前损失，则不需要缴付所得税，在合乎税法规定的条件下。企业的损失可以往将来的年度“前带”，也就是说来年的税前盈利可以先抵了过去的损失后，才计算所得税。
不一样的报表读者可能有不一样的目的，以上的逐步式损益表格式不见得合其目的。基于此点，美国公司便率先提供“两步式”损益表，第一步明列各项收入，第二步明列各项本钱及成本，前者之和减去后者之和，就是税前净利，再扣除所得税，得到税后净利。
这里要特别指出的是，损益表呈现的是企业的“会计损益”，而不是“现金收入支出”，比如巴士公司售出车资卡收进的现金并不是营业收入，而是“预收收入”，是流动负债，因此表现于资产负债表中的负债，而非损益表中的收入。要等持卡人搭车后，此部分的预收收入才变成车资收入。同样的，非属本会计年度的预付租金或预付保险费应以流动资产表现，不会出现于损益表中的成本项目。以会计术语来讲，损益表是依据“权责基础”编制的，以现金收入及支出为准的“现金基础”早就被淘汰了。1994年中国的会计规范“向界并轨”指的主要就是弃现金基础、采权责基础。