复式记账系统是会计规则中的第二条规则。它意味着在一笔交易中，在资产、负债或所有者权益中至少有两个变化。比如，如果一个投资者投资了15 000美元，那么资产(现金)就增加了15 000美元，所有者权益(实收资本)也将增加15 000美元。

复式记账的规则并不是指交易总能影响等式的两边——甚至只是等式的两个部分。一笔交易可能只影响等式左边而引起一项资产的增加和另一项资产的减少，例如用现金购买存货。一笔交易也可能只影响等式的右边。复式记账系统并没有特定的规则来确定等式方向的变化。等式左边和右边的总计数可能增加、减少甚至保持不变。但是最基本的是，在每笔交易后会计等式总是保持平衡。

具体来说，经济业务对会计等式的影响主要表现为以下几点:

(1)一项资产的增加和一项权益的增加;

(2)一项资产的减少和一项权益的减少;

(3)一项资产的增加和另一项资产的减少;

(4)一项权益的增加和另一项权益的减少。

我们将通过GRF公司发生的经济业务来看一看典型的业务对资产负债表等式的影响。

假定GRF公司于2008年1月1日成立，成立时拥有资产500 000美元，负债200 000美元，所有者权益(实收资本)300 000美元。会计等式为:

资产=负债+所有者权益

$500 000=$200 000+$300 000

GRF公司一月份发生的经济业务如下:

(1)1月3日，签发一张金额为12 000美元的票据，从银行取得贷款;

(2)1月5日，向雇员发行普通股1 000股，每股面值20美元，以现金方式收到;

(3)1月18日，以现金购买设备，金额1 250美元;

(4)1月19日，赊购存货，金额400美元;

(5)1月28日，以现金支付赊购款，金额300美元。

对会计等式在每笔交易后的分析见下表。

GRF公司2008年1月1日至1月31日交易分析表

从上表我们可以看出，每笔交易至少影响到两个账户。但是总资产总是等于总负债加上总所有者权益，也就是说，等式总是保持平衡。例如交易1中，贷款业务引起资产、现金、负债、应付票据同时增加12 000美元。当交易结束后，GRF公司拥有资产512 000美元(500 000美元+12 000美元)，负债212 000美元(200 000美元+12 000美元)和所有者权益300 000美元，等式两边是相等的。

Reading Material

Types of Assets

Assets may take many forms.While they may be grouped together into categories，as stated above，they may be considered to be tangible and intangible assets as well.A tangible asset is one that can be readily seen，and possibly touched，such as those previously illustrated and those in the first three categories listed below.They are physical assets.An intangible asset is without physical qualities，but has a value based on rights or privileges belonging to the owner.Two examples of intangible assets are patents and franchises.

The assets of an organization are usually divided into four categories:(1) current assets，(2)investments，(3)property，plant，and equipment，and(4) intangible assets.

Current assets are defined as cash and other assets that can reasonably be expected to be converted to cash，used up，or sold within 1 year or less.Examples of current assets include cash，accounts receivable(obligations due from customers)，and supplies.

Investments are generally of a long-term nature，are not used in the normal operations of the organization，and are not expected to be converted to cash within the year.Examples of investments are stocks and bonds of other organizations.

Property，plant，and equipment are long-term or long-life assets that are used in the continuing operations of the organization and are expected to be used by the organization for more than a year.These kinds of assets are also known as plant assets or fixed assets.Examples of these assets are land，buildings，machinery，and equipment.

Intangible assets are usually of a long-term nature and have no physical substance but are of value to the owners of the organization.Examples of these assets are copyrights，goodwill，and trademarks.