• Computing federal individual income tax liability has three major steps: measuring total income (adjusted gross income), converting total income to taxable income, and calculating taxes due.
计算联邦个人所得税的纳税义务有3个主要步骤：测算总所得（调整后所得总额），将总所得转换成应纳税所得，计算纳税义务。

• A traditional benchmark measure of income is the Haig-Simons definition: Income during a given period is the net change in the individual’s power to consume.
传统的收入基准测量是Haig-Simons定义：给定一段时间的收入就是个人消费能力的净变化。

• Implementation of the Haig-Simons criterion is confounded by several difficulties: (1) Income must be measured net of the expenses of earning it. (2) Unrealized capital gains and the imputed income from durable goods are not easily gauged. (3) It is difficult to measure the value of in-kind receipts. They are phased out at high-income levels. Itemized deductions change after-tax relative prices, which often affects economic behavior.
Haig-Simons标准在实现时遇到了一些困难：（1）所得必须是除去获得它的开销之后的净所得。（2）未实现的资本盈利和耐用品的归算所得不容易测量。（3）难以测量实物收入的价值。它们在高收入水平上是按收入递减的。逐项扣税改变了税后的相对价格，这常常会影响经济行为。

• Major itemized deductions in the US tax code include (1) unreimbursed medical expenses in excess of 7.5 percent of AGI, (2) state and local income and property taxes, (3) certain interest expenses, (4) charitable contributions.
美国税制中主要的逐项扣税包括（1）未退税的医疗支出 > 7.5% AGI，（2）州和本地所得税和物业税，（3）某些利息支出，（4）慈善捐赠

• Tax expenditures are the revenues forgone due to preferential tax treatment.
税式支出是为了税收优惠而放弃的收入。

• The final step in determining tax liability is to apply a schedule of rates to taxable income. Because of various phaseouts, the actual statutory marginal tax rates exceed the official rates.
确定纳税义务的最后一步是对应纳税收入应用税率清单。因为各种扣税递递的缘故，实际的法定边际税率超过了官方税率。

• The alternative minimum tax (AMT) was designed to make sure that high-income taxpayers who heavily utilize tax shelters would pay at least some federal income tax. However, due to certain structural flaws, it will soon be the tax system confronting millions of middle-class Americans.
替代最低税（AMT）的设计目的是确保高收入的纳税人大量运用避税手段时，至少会交一些联邦所得税。但是，由于某些结构上的缺陷，它很快就将成为面对数百万美国中产阶级的税收系统。

• Critics of the Haig-Simons criterion argue that it guarantees neither fair nor efficient outcomes.
Haig-Simons标准的批评者称，它既不能保证公平也不能保证效率。

• The US income tax base excludes: (1) interest on state and local bonds, (2) employer contributions to pension and medical plans, (3) gifts and inheritances.
美国所得税基不包括：（1）州和地方债券的利息，（2）雇主对养老金和医疗计划的贡献，（3）礼物和继承。

• Exemptions are fixed amounts per family member. Exemptions are subtracted from adjusted gross income (AGI) and phased out at high-income levels.
免税额对每个家庭成员是固定的数额。免税额要从调整后的所得总额（AGI）中减去，并在高收入水平上递减。

• Deductions are either standard or itemized. A standard deduction reduces taxable income by a fixed amount.
扣税要么是标准的，要么是逐项的。标准扣税在应纳税所得中减去一个固定数额。

• Itemized deductions are permitted for expenditures on particular goods and services.
逐项扣税适用于某些特定商品和服务的支出。

• Bracket widths, personal exemptions, the standard deduction, and the earned income credit are now indexed against inflation. However, there are no provisions to correct for inflation's effect on the taxation of capital income.
税级宽度、个人免税、标准扣税和收入所得计算现在是根据通涨指数化的。但是，没有条款来修正通涨对资本收入税的影响。

• No system of family taxation can simultaneously achieve increasing marginal tax rates, marriage neutrality, and equal taxes for families with equal incomes. Under current law, joint tax liabilities may increase or decrease upon marriage, depending on the couple's circumstances.
没有哪个多税种税收系统可以同时实现增加的边际税率、与婚姻无关，以及相等收入的家庭交相等的税。在当前的法律下，夫妻共同的纳税义务在结婚前后可能增长或下降，这取决于夫妻的具体情况。

• The United States follows a global system with respect to the tax treatment of income earned in other countries. The total amount of tax due is supposed to be roughly independent of whether the income is earned at home or abroad.
美国采取的是全球系统，考虑到在其他国家所得的征税。应交税款基本上与在国内或国外取得收入无关。

• Income tax systems are important as revenue raisers for the states. State income taxes have lower rates than the federal system and vary widely in their exact provisions.
作为美国收入的筹集系统，所得税系统很重要。州所得税比联邦所得税的税率低一些，在具体的规定方面变化很大。


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