Federal Individual Income Tax Terms:
An Explanation
Updated February 4, 2021
Congressional Research Service
https://crsreports.congress.gov
RL30110

Federal Individual Income Tax Terms: An Explanation

Summary
This report describes the terms most commonly used when discussing the federal individual
income tax. Most of these tax terms are explained in the order that they occur in the process of
determining one’s income tax on the Form 1040.
Total income is the sum total of al income required to be reported for tax purposes. Total income
does not include exclusions, items specifical y excluded from determination of gross income.
Total income may be reduced by certain adjustments to income for special types of expenses that
Congress has determined should be considered in calculating gross income. These adjustments,
often referred to as above-the-line deductions, can general y be claimed by al eligible taxpayers,
not just those who itemize deductions. For 2020 and 2021, taxpayers who do not itemize their
deductions can claim an additional deduction for charitable contributions.
Adjusted gross income (AGI) equals gross income less above-the-line deductions (i.e., qualifying
adjustments to income). It is the income measurement before a taxpayer claims either the
standard deduction or the sum of al their itemized deductions (whichever is greater). Itemized
deductions are subtracted from AGI and are al owed for certain types of expenditures for which
income taxation is deemed inappropriate or inadvisable. The standard deduction, by contrast, is a
set amount that varies by filing status and may be subtracted from AGI if it is greater than a
taxpayer’s itemized deductions. An additional standard deduction amount is available to certain
individuals, for example the blind or elderly. Deductions function like adjustments and exclusions
in their effect on tax liability.
Taxable income is adjusted gross income reduced by either the standard deduction (plus the
additional standard deduction in some cases) or itemized deductions along with a deduction for
qualified pass-through business income, when applicable. Taxable income is the base to which the
income tax rates are applied to calculate income tax liability. Tax liability is calculated by
applying the marginal tax rate and schedule to taxable income. Tax credits are then subtracted
from gross tax liability to arrive at a taxpayer’s final tax liability. Hence, tax credits reduce tax
liability directly, on a dollar-for-dollar basis. Tax credits are available to al qualifying taxpayers,
whether they itemize deductions or not.
Total tax liability is the amount of federal income tax owed by the taxpayer to the federal
government. When a taxpayer’s final tax liability exceeds federal taxes withheld, estimated
quarterly taxes paid, and certain other credits, then the taxpayer has taxes due and must pay the
federal government additional federal income taxes to cover the shortfal . A refund is a payment
by the federal government to a taxpayer whose withheld taxes and/or estimated tax payments or
refundable credits exceeded final tax liability.
A copy of the most recent version of income tax return to date, the 2020 IRS Form 1040, is
included at the end of this report.
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Introduction
This report describes the terms most commonly used when discussing the federal individual
income tax.1 The structure of this report follows the general order of the IRS Form 1040—the
form individuals use to determine their income tax. Tax forms can change, and al references in
this report are to the 2020 Form 1040.2 Many taxpayers determine their tax liability with the use
of tax preparation software (e.g., TurboTax®) and paid tax preparers, which eliminates the need
to be familiar with the Form 1040. Therefore, taxpayers who rely on tax preparation software or
services may not be familiar with some of the concepts presented in this report.
Total Income
Total income, also sometimes referred to as gross income, is the broadest measure of income used
for tax purposes. It is the total of al realized income recognized by the tax law. It is measured net
of business expenses but before any other deductions or adjustments. It includes employee
compensation such as wages, salaries, and tips; taxable interest and dividend income; business
and farm income (net of expenses); realized capital gains; income from rents, royalties, trusts,
estates, and partnerships; and taxable pensions and annuities.
Gross income does not include income explicitly excluded from tax. An exclusion is an item of
income that is not included as income for tax purposes because the tax code explicitly excludes—
or exempts—it from taxation.3 Examples of items of income which are exempt from federal
income taxation and, hence, excluded from gross income, are state and local bond interest
income, public assistance (welfare), smal gifts, employer contributions for health care, and
employer-provided contributions to retirement plans. Social Security and Railroad Retirement
income may or may not be excluded from income subject to tax.4 The taxability of Social
Security and Railroad Retirement depends on the amount of other income the taxpayer receives.
Other forms of income excluded from taxation are a clergy member’s tax-free housing al owance,
qualified foster care payments, and qualified scholarship and fel owship grants. Under certain
conditions, a taxpayer can exclude a limited amount of disability pay such as workers’
compensation. Except for tax-exempt interest, exclusions general y are not required to be reported
to the Internal Revenue Service.

1 Economic income is the broadest measure of all income, and is an economic concept rather than one contained in the
tax code. It is defined as realized monetary compensation plus the value of any other nonmonetary forms of
compensation that an individual receives. For example, in addition to the salary employees receive each year, they may
also receive compensation in the form of health insurance premiums paid for by their employer. T his employee’s
economic income is their salary plus the monetary value of the insurance premiums paid for by their employer.
Economic income, therefore, is a measure of an individual’s total compensation. Another example of economic but not
monetary income is the imputed rental value of owner-occupied housing, which is not subject to taxation.
Understanding economic income is important for constructing tax policies that are efficient and equitable. Economic
income is not listed explicitly on the Form 1040 found in Appe ndix A.
2 For official copies of the latest 1040, see Internal Revenue Service, About Form 1040, U.S. Individual Income Tax
Return, at https://www.irs.gov/forms-pubs/about-form-1040.
3 T he expression “tax-exempt” is used to describe types of income and organizations that are not subject to taxation.
Interest income from state and local bonds, for example, is exempt from federal income taxes. Certain qualifying
nonprofit organizations are exempt from federal income taxation. T he provisions are not, however, described as
exemptions on the tax return. They are more properly termed “ exclusions.”
4 For more information on the taxability of Social Security benefits, see CRS Report RL32552, Social Security:
Taxation of Benefits, by Paul S. Davies.
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A taxpayer’s gross income is listed on line 9 of the Form 1040 found in Appendix A. Exclusions
are not listed explicitly on the Form 1040.
Adjustments to Income (Above-the-Line
Deductions)
Adjustments to income, also known as above-the-line deductions, are al owed for certain
payments made by the taxpayer and are general y related to the earning of income. These
payments are deducted from gross income in arriving at adjusted gross income. Examples of
payments that may qualify for an above-the-line deduction include contributions to Keogh or
traditional (but not Roth) individual retirement accounts (IRAs), forfeited penalties on early
withdrawals of savings, and interest paid on student loans. Adjustments to income function
similarly to deductions that are applied later in the calculation of taxable income (i.e., itemized
deductions or the standard deduction). However, unlike these deductions, above-the-line
deductions can general y be claimed by al qualified taxpayers, whether or not they use the
standard deduction or itemize deductions (see “Deductions”).5
The sum of the taxpayer’s adjustments to income is listed on line 10c of the Form 1040. The
majority of a taxpayer’s total adjustments to income are listed on lines 10 to 21 of Schedule 1
found in Appendix A. For 2020 and 2021, nonitemizers may claim an additional temporary
deduction for charitable contributions. This amount is listed on line 10b of the Form 1040.
Adjusted Gross Income (AGI)
Adjusted gross income (AGI) is equal to a taxpayer’s total income minus adjustments to income.
AGI is the basic measure of income under the federal income tax and is the income measurement
before deductions are taken into account.6 AGI is commonly used as the base for computing many
of the limits under the tax law, such as those on the itemized deduction for medical and dental
expense and miscel aneous itemized deductions.
A taxpayer’s adjusted gross income is listed on line 11 of the Form 1040.
Deductions
Deductions from adjusted gross income are al owed for certain types of expenditures of income.
Deductions may be claimed in one of two ways. First, taxpayers can choose to itemize (explicitly
list) their deductible expenses. Itemized deductions are al owed for many purposes, including
certain medical expenses; state and local property taxes, income (or sales) taxes, and a few other
taxes; home mortgage interest, points, and limited amounts of other interest paid (but not personal

5 T here is an additional deduction amount for charitable giving in 2020 that is only available to nonitemizers. For more
information, see CRS In Focus IF11022, The Charitable Deduction for Individuals, by Margot L. Crandall-Hollick and
Molly F. Sherlock; and CRS Insight IN11420, Tem porary Enhancements to Charitable Contributions Deductions in the
CARES Act, by Jane G. Gravelle.
6 P.L. 115-97 substantially changed the individual income tax system, including by temporarily suspending personal
exemptions from 2018 through the end of 2025. Before 2018, tax payers deducted personal exemptions from their AGI
when calculating taxable income. Personal exemptions were allowed for taxpayers, spouse s, and any dependents. For
2020, the personal exemption amount would have been $4,300 per exemption. Absent any legisl ative change, personal
exemptions will again be in effect beginning in 2026.
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interest); contributions to charitable organizations; certain casualty and theft losses; and a few
other “miscel aneous” expenses.
Alternatively, a taxpayer can choose to claim the standard deduction, which was intended to
reduce the complexity of paying taxes. The standard deduction varies depending on filing status
(single, married filing jointly, head of household), whether the taxpayer is over 65, and whether
the taxpayer is blind. For 2020 the standard deductions were as follows: $24,800 for married
taxpayers filing jointly or qualified widow(er)s; $12,400 for single taxpayers; and $18,650 for
taxpayers who qualify as the head of a household. The standard deductions for those who are 65
or older and for those who are legal y blind are increased by $1,650 if single or head of household
and $1,300 if married filing jointly. These increases apply per classification. Thus, a 70-year-old
blind and single taxpayer would be eligible for a $3,300 ($1,650 plus $1,650) increase in his or
her standard deduction. These amounts are adjusted annual y for inflation.
Only individuals with deductions that can be itemized in excess of the standard deduction find it
worthwhile to itemize. These tend to be taxpayers in the middle- to high-income ranges. In the
2018 tax year (the most recent data available), 11.4% of taxpayers itemized their deductions.7
Whichever deduction the taxpayer claims—total itemized or standard—the deduction amount is
subtracted from AGI.
Additional y, individuals with pass-through business income may deduct up to 20% of their
qualified business income when determining their taxable income through 2025. This deduction
is often referred to as the 199A deduction and is subtracted from AGI after either total itemized
deductions or the standard deduction.8 Pass-through businesses include sole proprietorships,
partnerships, and S corporations. Pass-through owners pay taxes on their share of the business’s
income according to the individual income tax rates. In contrast, the income of C corporations is
taxed once at the corporate level according to the corporate tax system, and then a second time at
the individual-shareholder level.
Deductions function like adjustments and exclusions in their effect on tax liability. Deductions
reduce a taxpayer’s tax liability, but only by a percentage of the amount deducted. An individual
in the 35% tax bracket would receive a reduction in taxes of $35 for each $100 deduction while
an individual in the 24% tax bracket would receive a reduction in taxes of $24 for each $100
deduction. Hence, the same deduction can be worth different amounts to different taxpayers
depending on their marginal tax bracket. More simply stated, the tax savings from deductions are
general y equal to the taxpayer’s tax rate times the amount of the deduction. So higher-income
taxpayers typical y benefit more than lower-income taxpayers from deductions.
A taxpayer’s standard or total itemized deductions are listed on line 12 of the Form 1040. The
individual components of the itemized deduction are listed on lines 1 to 16 on Schedule A to
Form 1040 in Appendix A. The 199A deduction for qualified business income, if applicable, is
listed on line 13 of the Form 1040.
Taxable Income
Taxable income, the narrowest measure of income used on the income tax return, is equivalent to
adjusted gross income reduced by either the standard deduction or itemized deduction and the

7 CRS calculations using 2018 Internal Revenue Service, Statistics of Income, T able 1.2.
8 For more information on the 199A deduction, see CRS In Focus IF11122, Section 199A Deduction for Pass-through
Business Incom e: An Overview, by Gary Guenther.
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personal exemption. Taxable income is the base upon which the income tax rates are applied to
calculate income tax liability.
Taxable income is listed on line 15 of the Form 1040.
Tax Liability
Tax liability, also sometimes referred to as gross tax liability, is a taxpayer’s tax liability prior to
the subtraction of tax credits. For most taxpayers, gross tax liability is equal to regular income tax
liability, which is calculated by applying the marginal tax rate schedule to taxable income. The
structure of the marginal tax rate schedule is progressive, which means higher-earning taxpayers
face higher tax rates on the last dollar that they earn. To understand how the marginal tax
structure is applied, consider the 2020 marginal tax rate schedule provided in Appendix B.9 The
2020 tax schedule shows the various tax rates and income ranges to which those rates are applied.
A married couple with a taxable income of $80,000 would fal into the 12% tax bracket. This
means that the first $19,750 of their taxable income would be taxed at a rate of 10%, their next
$60,250 of income would be taxed at 12%.
A smal fraction of taxpayers (0.1% in 2019) must also account for the alternative minimum tax
(AMT) when computing their gross tax liability.10 The AMT is calculated in the following
manner. First, an individual adds back certain tax deductions and tax preference items to taxable
income. This amount then becomes the AMT tax base. Next, a basic exemption is al owed and
subtracted from the AMT tax base. A two-tiered tax rate structure of 26% and 28% is then
assessed against the remaining AMT tax base to determine the AMT liability. If the AMT liability
exceeds a taxpayer’s regular income liability a taxpayer must add the difference between the two
to their regular income tax liability to arrive at gross tax liability. Congress, in 1969, enacted the
predecessor to the current individual AMT to make sure that everyone paid at least a minimum of
taxes and stil preserve the economic and social incentives in the tax code.11
A taxpayer’s regular income tax liability is listed on line 16 of the Form 1040. The AMT liability
is listed on line 1 of Schedule 2 of the Form 1040 in Appendix A. A taxpayer’s gross tax liability
is listed on line 18 of the Form 1040.
Nonrefundable Credits
Nonrefundable tax credits are subtracted from gross tax liability to arrive at a taxpayer’s final tax
liability. Thus, nonrefundable tax credits reduce an individual’s tax liability directly, on a dollar-
for-dollar basis, and are available to al qualified taxpayers. A taxpayer may not claim more
nonrefundable tax credits than his or her tax liability. Therefore, the only time in which
nonrefundable tax credits do not result in a dollar-for-dollar reduction in an individual’s tax
liability is when the amount of nonrefundable tax credits exceeds the individual’s tax liability. A
different class of tax credits, known as refundable tax credits, can be claimed even when they
exceed an individual’s tax liability. Refundable tax credits are discussed later in this report.

9 For more information, see CRS Insight IN11530, The Federal Income Tax: How Do Marginal Income Tax Rates
Work in 2020?, by Margot L. Crandall-Hollick.
10 T ax Policy Center, “Who pays the AMT ?,” updated May 2020, at https://www.taxpolicycenter.org/briefing-book/
who-pays-amt.
11 For more information, see CRS Report R44494, The Alternative Minimum Tax for Individuals: In Brief, by Donald J.
Marples.
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Examples of nonrefundable credits are the credit for the elderly and the permanently and total y
disabled, the credit for child and dependent care expenses, and the foreign tax credit.12
The total amount of nonrefundable tax credits is found on line 21 of the Form 1040. The
individual nonrefundable tax credits are listed on Schedule 3 to Form 1040 in Appendix A.
Total Tax Liability
Total tax liability, also sometimes referred to as final tax liability, is the amount of federal income
tax owed by the taxpayer to the federal government after taking into account al owable refundable
tax credits. Thus, total tax liability represents the taxpayer’s total federal income tax bil for the
tax year.
A taxpayer’s total tax liability is found on line 24 of the Form 1040.
Payments
Most taxpayers make periodic tax payments throughout the year via income withholdings that are
credited against their federal income tax liability. Employees typical y have a certain percentage
of their paycheck withheld (W-2 withholding, named for the IRS Form W-2) each pay period by
their employer. Taxpayers who receive nonwage or nonemployee compensation income, such as
interest or dividend payments, debt cancelation, and certain other types of income, may have a
fraction of this income withheld (1099 withholding, again, named for IRS Form 1099) by the
compensating party.13 The withheld amounts are then forwarded to the IRS.
Some taxpayers make estimated tax payments throughout the year—typical y quarterly. There are
a variety of reasons why estimated tax payments may be required—for example, when the
taxpayer earns income not subject to withholding or when there is an expectation that a taxpayer
may owe more than a certain amount in taxes even after accounting for withholdings and credits.
A taxpayer estimates the taxes owed on the income he or she earned in a particular quarter and
pays this amount during the year rather than waiting until April 15 of the following year.
Refundable tax credits are another form of tax “payment.” Refundable tax credits are similar to
nonrefundable tax credits except that a taxpayer may claim refundable tax credits in an amount
greater than his or her tax liability. When the amount of refundable credits exceeds a taxpayer’s
tax liability, the Treasury makes a direct payment to the taxpayer for the difference. The primary
refundable credits are the earned income tax credit and the child tax credit.14
A taxpayer’s total tax payment is found on line 33 of the Form 1040.

12 For more information, see CRS Report R44993, Child and Dependent Care Tax Benefits: How They Work and Who
Receives Them , by Margot L. Crandall-Hollick and Conor F. Boyle.
13 Starting in 2020, those with nonemployee compensation (i.e., independent contractors) have had such income
reported on Form 1099-NEC.
14 For more information, see CRS Report R43805, The Earned Income Tax Credit (EITC): How It Works and Who
Receives It, by Margot L. Crandall-Hollick, Gene Falk, and Conor F. Boyle; and CRS Report R41873, The Child Tax
Credit: How It Works and Who Receives It, by Margot L. Crandall-Hollick.
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Federal Individual Income Tax Terms: An Explanation

Tax Refund
A tax refund is a payment by the federal government to a taxpayer whose withheld taxes,
estimated tax payments, and refundable credits exceeded final tax liability, entitling him or her to
a refund for overpayment of the tax bil .
The amount of refunded taxes owed to a taxpayer may be found on line 34 of the Form 1040.
Amount Owed
When a taxpayer’s total tax liability exceeds federal taxes withheld, estimated tax payments, and
refundable credits, then the taxpayer wil owe the federal government an additional amount to
cover the shortfal in paid taxes.
Taxes owed are found on line 37 of the Form 1040.
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Federal Individual Income Tax Terms: An Explanation

Appendix A. 2020 IRS Form 1040

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Federal Individual Income Tax Terms: An Explanation

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Federal Individual Income Tax Terms: An Explanation

2020 IRS Schedule 1 (Form 1040)

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Federal Individual Income Tax Terms: An Explanation

2020 IRS Schedule 2 (Form 1040)

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Federal Individual Income Tax Terms: An Explanation

2020 IRS Schedule 3 (Form 1040)

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Federal Individual Income Tax Terms: An Explanation

2020 IRS Schedule A (Form 1040)

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Federal Individual Income Tax Terms: An Explanation

Appendix B. 2020 Marginal Tax Rate Schedule
Table 1. Statutory Marginal Tax Rates, 2020
Tax Schedules by Filing Status
Married Filing Jointly

If taxable income is:
Then, tax is:
$0
to
$19,750
10% of the amount over $0
$19,750
to
$80,250
$1,975 plus 12% of the amount over $19,750
$80,250
to
$171,050
$9,235 plus 22% of the amount over $80,250
$171,050
to
$326,600
$29,211 plus 24% of the amount over $171,050
$326,600
to
$414,700
$66,543 plus 32% of the amount over $326,600
$414,700
to
$622,050
$94,735 plus 35% of the amount over $414,700
$622,050 plus

$167,307.50 plus 37% of the amount over $622,050
Single
If taxable income is:
Then, tax is:
$0
to
$9,875
10% of the amount over $0
$9,875
to
$40,125
$987.50 plus 12% of the amount over $9,875
$40,125
to
$85,525
$4,617.50 plus 22% of the amount over $40,125
$85,525
to
$163,300
$14,605.50 plus 24% of the amount over $85,525
$163,300
to
$207,350
$33,271.50 plus 32% of the amount over $163,300
$207,350
to
$518,400
$47,367.50 plus 35% of the amount over $207,350
$518,400 plus

$156,235 plus 37% of the amount over $518,400
Heads of Households
If taxable income is:
Then, tax is:
$0
to
$14,100
10% of the amount over $0
$14,100
to
$53,700
$1,410 plus 12% of the amount over $14,100
$53,700
to
$85,500
$6,162 plus 22% of the amount over $53,700
$85,500
to
$163,300
$13,158 plus 24% of the amount over $85,500
$163,300
to
$207,350
$31,830 plus 32% of the amount over $163,300
$207,350
to
$518,400
$45,926 plus 35% of the amount over $207,350
$518,400 plus

$154,793.50 plus 37% of the amount over $518,400
Source: Internal Revenue Code.
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Federal Individual Income Tax Terms: An Explanation

Author Information

Mark P. Keightley

Specialist in Economics

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Congressional Research Service
RL30110 · VERSION 16 · UPDATED
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