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The Tax Policy Center's

Briefing Book

A citizen’s guide to the fascinating (though often complex) elements of the US tax system.

Tax Policy Center Briefing Book

Key Elements of the U.S. Tax System

  • Briefing Book
  • Individual Income Tax
  • How do phaseouts of tax provisions affect taxpayers?
  • Chapters
    • Introduction
      • Introduction
        • Introduction
    • Some Background
      • Federal Budget
        • What are the sources of revenue for the federal government?
        • How does the federal government spend its money?
        • What is the breakdown of revenues among federal, state, and local governments?
        • How do US taxes compare internationally?
      • Federal Budget Process
        • How does the federal budget process work?
        • What is the history of the federal budget process?
        • What is the schedule for the federal budget process?
        • What is reconciliation?
        • How is a budget resolution enforced?
        • What is PAYGO?
        • What are rescissions?
      • Federal Budget Outlook
        • How accurate are long-run budget projections?
        • What have budget trends been over the short and long term?
        • How much spending is uncontrollable?
        • What are tax extenders?
        • What options would increase federal revenues?
        • What does it mean for a government program to be off-budget?
        • How did the TCJA affect the federal budget outlook?
      • Taxes and the Economy
        • How do taxes affect the economy in the short run?
        • How do taxes affect the economy in the long run?
        • What are dynamic scoring and dynamic analysis?
        • Do tax cuts pay for themselves?
        • On what do economists agree and disagree about the effects of taxes on economic growth?
        • What are the economic effects of the Tax Cuts and Jobs Act?
      • Economic Stimulus
        • What is the role of monetary policy in alleviating economic downturns?
        • What are automatic stabilizers and how do they work?
        • What characteristics make fiscal stimulus most effective?
      • Distribution of Tax Burdens
        • How are federal taxes distributed?
        • Are federal taxes progressive?
        • How should progressivity be measured?
        • What is the difference between marginal and average tax rates?
        • What criticisms are levied against standard distributional analysis?
        • How should distributional tables be interpreted?
        • Who bears the burden of the corporate income tax?
        • Who bears the burden of federal excise taxes?
        • How do financing methods affect the distributional analyses of tax cuts?
        • How do taxes affect income inequality?
      • Tax Expenditures
        • What are tax expenditures and how are they structured?
        • What is the tax expenditure budget?
        • Why are tax expenditures controversial?
        • What are the largest tax expenditures?
        • How did the TCJA affect tax expenditures?
      • Tax Gap and Tax Shelters
        • What is the tax gap?
        • What does the IRS do and how can it be improved?
        • What is a tax shelter?
      • Recent History of the Tax Code
        • What did the 2008–10 tax stimulus acts do?
        • What did the American Taxpayer Relief Act of 2012 do?
        • How did the Tax Cuts and Jobs Act change personal taxes?
        • How did the Tax Cuts and Jobs Act change business taxes?
    • Key Elements of the U.S. Tax System
      • Individual Income Tax
        • What is the standard deduction?
        • What are itemized deductions and who claims them?
        • How did the TCJA change the standard deduction and itemized deductions?
        • What are personal exemptions?
        • How do federal income tax rates work?
        • What are tax credits and how do they differ from tax deductions?
        • How do phaseouts of tax provisions affect taxpayers?
      • Capital Gains and Dividends
        • How are capital gains taxed?
        • What is the effect of a lower tax rate for capital gains?
        • What is carried interest, and how is it taxed?
        • How might the taxation of capital gains be improved?
      • AMT
        • What is the AMT?
        • Who pays the AMT?
        • How much revenue does the AMT raise?
        • How did the TCJA change the AMT?
      • Taxes and the Family
        • What is the child tax credit?
        • What is the adoption tax credit?
        • What is the earned income tax credit?
        • Do all people eligible for the EITC participate?
        • How does the tax system subsidize child care expenses?
        • What are marriage penalties and bonuses?
        • How did the TCJA change taxes of families with children?
      • Taxes and the Poor
        • How does the federal tax system affect low-income households?
        • What is the difference between refundable and nonrefundable credits?
        • Can poor families benefit from the child tax credit?
        • Why do low-income families use tax preparers?
        • How does the earned income tax credit affect poor families?
        • What are error rates for refundable credits and what causes them?
        • How do IRS audits affect low-income families?
      • Taxes and Retirement Saving
        • What kinds of tax-favored retirement arrangements are there?
        • How large are the tax expenditures for retirement saving?
        • What are defined benefit retirement plans?
        • What are defined contribution retirement plans?
        • What types of nonemployer-sponsored retirement savings accounts are available?
        • What are Roth individual retirement accounts?
        • Who uses individual retirement accounts?
        • How does the availability of tax-favored retirement saving affect national saving?
        • What’s the difference between front-loaded and back-loaded retirement accounts?
        • What is an automatic 401(k)?
        • How might low- and middle-income households be encouraged to save?
      • Taxes and Charitable Giving
        • What is the tax treatment of charitable contributions?
        • What entities are tax-exempt?
        • Who benefits from the deduction for charitable contributions?
        • How would various proposals affect incentives for charitable giving?
        • How large are individual income tax incentives for charitable giving?
        • How did the TCJA affect incentives for charitable giving?
      • Taxes and Health Care
        • How much does the federal government spend on health care?
        • Who has health insurance coverage?
        • Which tax provisions subsidize the cost of health care?
        • How does the tax exclusion for employer-sponsored health insurance work?
        • What are premium tax credits?
        • What tax changes did the Affordable Care Act make?
        • How do health savings accounts work?
        • How do flexible spending accounts for health care expenses work?
        • What are health reimbursement arrangements and how do they work?
        • How might the tax exclusion for employer-sponsored health insurance (ESI) be reformed?
      • Taxes and Homeownership
        • What are the tax benefits of homeownership?
        • Do existing tax incentives increase homeownership?
      • Taxes and Education
        • What tax incentives exist for higher education?
        • What tax incentives exist to help families pay for college?
        • What tax incentives exist to help families save for education expenses?
        • What is the tax treatment of college and university endowments?
      • Tax Complexity
        • Why are taxes so complicated?
        • What are the benefits of simpler taxes?
        • What policy reforms could simplify the tax code?
      • Wealth Transfer Taxes
        • How do the estate, gift, and generation-skipping transfer taxes work?
        • Who pays the estate tax?
        • How many people pay the estate tax?
        • What is the difference between carryover basis and a step-up in basis?
        • How could we reform the estate tax?
        • What are the options for taxing wealth transfers?
        • What is an inheritance tax?
      • Payroll Taxes
        • What are the major federal payroll taxes, and how much money do they raise?
        • What is the unemployment insurance trust fund, and how is it financed?
        • What are the Social Security trust funds, and how are they financed?
        • Are the Social Security trust funds real?
        • What is the Medicare trust fund, and how is it financed?
      • Excise Taxes
        • What are the major federal excise taxes, and how much money do they raise?
        • What is the Highway Trust Fund, and how is it financed?
      • Energy and Environmental Taxes
        • What tax incentives encourage energy production from fossil fuels?
        • What tax incentives encourage alternatives to fossil fuels?
        • What is a carbon tax?
      • Business Taxes
        • How does the corporate income tax work?
        • What are pass-through businesses?
        • How are pass-through businesses taxed?
        • Is corporate income double-taxed?
      • Tax Incentives for Economic Development
        • What is the new markets tax credit, and how does it work?
        • What is the Low-Income Housing Tax Credit and how does it work?
        • What are Opportunity Zones and how do they work?
      • Taxes and Multinational Corporations
        • How does the current system of international taxation work?
        • How do US corporate income tax rates and revenues compare with other countries’?
        • What are the consequences of the new US international tax system?
        • How does the tax system affect US competitiveness?
        • How would formulary apportionment work?
        • What are inversions, and how will TCJA affect them?
        • What is a territorial tax and does the United States have one now?
        • What is the TCJA repatriation tax and how does it work?
        • What is the TCJA base erosion and anti-abuse tax and how does it work?
        • What is global intangible low-taxed income and how is it taxed under the TCJA?
        • What is foreign-derived intangible income and how is it taxed under the TCJA?
    • How Could We Improve the Federal Tax System?
      • Comprehensive Tax Reform
        • What is comprehensive tax reform?
        • What are the major options for comprehensive tax reform?
      • Broad-Based Income Tax
        • What is a broad-based income tax?
        • What would and would not be taxed under a broad-based income tax?
        • What would the tax rate be under a broad-based income tax?
      • National Retail Sales Tax
        • What is a national retail sales tax?
        • What would and would not be taxed under a national retail sales tax?
        • What would the tax rate be under a national retail sales tax?
        • What is the difference between a tax-exclusive and tax-inclusive sales tax rate?
        • Who bears the burden of a national retail sales tax?
        • Would tax evasion and avoidance be a significant problem for a national retail sales tax?
        • What would be the effect of a national retail sales tax on economic growth?
        • What transition rules would be needed for a national retail sales tax?
        • Would a national retail sales tax simplify the tax code?
        • What can state and local sales taxes tell us about a national retail sales tax?
        • What is the experience of other countries with national retail sales taxes?
        • What did the President’s Advisory Panel on Federal Tax Reform say about the national retail sales tax?
      • Value Added Tax (VAT)
        • What is a VAT?
        • How would a VAT be collected?
        • What would and would not be taxed under a VAT?
        • What would the tax rate be under a VAT?
        • What is the difference between zero rating and exempting a good in the VAT?
        • Who would bear the burden of a VAT?
        • Is the VAT a money machine?
        • How would small businesses be treated under a VAT?
        • What is the Canadian experience with a VAT?
        • Why is the VAT administratively superior to a retail sales tax?
        • What is the history of the VAT?
        • How are different consumption taxes related?
      • Other Comprehensive Tax Reforms
        • What is the flat tax?
        • What is the X-tax?
      • Recent Comprehensive Tax Reform Proposals
        • Simple, Fair, and Pro-Growth: Proposals to Fix America’s Tax System, Report of the President’s Advisory Panel on Federal Tax Reform, November 2005
        • The Moment of Truth: Report of the National Commission on Fiscal Responsibility and Reform, December 2010
        • Debt Reduction Task Force, “Restoring America’s Future,” Bipartisan Policy Center, November 2010
        • The Tax Reform Act of 2014: Fixing Our Broken Tax Code So That It Works for American Families and Job Creators, House Ways and Means Committee
        • The Graetz Competitive Tax Plan, Updated for 2015
      • Return-Free Tax Filing
        • What is return-free filing and how would it work?
        • What are the benefits of return-free filing?
        • What are the drawbacks of return-free filing?
        • How would the tax system need to change with return-free filing?
        • Who would qualify for return-free filing?
        • Would return-free filing raise taxes?
        • What was the experience with return-free filing in California?
        • What other countries use return-free filing?
    • The State of State (and Local) Tax Policy
      • State and Local Revenues
        • What are the sources of revenue for state governments?
        • What are the sources of revenue for local governments?
      • Specific State and Local Taxes
        • How do state and local individual income taxes work?
        • How do state and local sales taxes work?
        • How do state and local property taxes work?
        • How do state and local corporate income taxes work?
        • How do state estate and inheritance taxes work?
        • How do state earned income tax credits work?
        • How do state and local severance taxes work?
        • How do state and local soda taxes work?
        • How do marijuana taxes work?
      • Fiscal Federalism and Fiscal Institutions
        • How does the deduction for state and local taxes work?
        • What are municipal bonds and how are they used?
        • What types of federal grants are made to state and local governments and how do they work?
        • What are state rainy day funds, and how do they work?
        • What are tax and expenditure limits?
        • What are state balanced budget requirements and how do they work?
    • Glossary
      • Glossary
        • Glossary

How do phaseouts of tax provisions affect taxpayers?

Individual Income Tax

<7/7
Q.

How do phaseouts of tax provisions affect taxpayers?

A.

Many preferences in the tax code phase out for high-income taxpayers—their value falls as income rises. Phaseouts narrow the focus of tax benefits to low- and middle-income households while limiting revenue costs, but raise marginal tax rates for affected taxpayers.

Many preferences in the tax code phase out for higher-income taxpayers, meaning their value declines after income reaches a certain level. Phaseouts target tax benefits on middle- and lower-income households and limit the loss of revenue. Phaseouts, however, not only claw back benefits from the more affluent, but also increase the effective marginal tax rate these taxpayers face, decreasing the after-tax gains of earning more income.

Some taxpayers are affected by multiple tax provisions phasing out at the same time, compounding the negative impact on their earning incentives. More broadly, phaseouts complicate the tax code and make taxes more difficult to understand.

HOW DO PHASEOUTS WORK?

Phaseouts are structured in different ways and thus have different effects. Some reduce credits and thus have the same impact on all affected taxpayers. Others reduce deductions, in which case their dollar impact depends on the taxpayer’s marginal tax rate: the higher the tax rate, the greater the value of the lost deduction.

Phaseouts reduce tax benefits at different rates depending on their structure and range. Most phaseouts reduce benefits at a constant rate over an income range; that rate depends on the width of the range. For example, for single tax filers, the American Opportunity Tax Credit phases out evenly over a $10,000 range, so the maximum $2,500 credit phases out at a 25 percent rate ($25 per $100 of income above the phaseout thresholds). In contrast, the adoption credit phases out over a $40,000 range, so the maximum $14,300 credit phases out at about a 35 percent rate ($35.75 per $100 of income above the threshold).

Some phaseouts, however, reduce benefits by a specified amount for each fixed increment of income. For example, the child tax credit decreases by $50 for every $1,000 or part of $1,000 in additional income above the phaseout threshold. Whether income exceeds the threshold by $1 or by $999, the credit falls by the same $50, so earning a few more dollars could make a taxpayer worse off.

Some phaseouts have more pronounced cliffs, so the benefit drops in large increments when income exceeds the threshold. For example, in 2020, the limit on the deduction for higher education tuition and fees drops from $4,000 to $2,000 for a single tax filer whose income exceeds $65,000 by even $1. Then the limit drops to zero for filers whose income tops $80,000. Again, just a few dollars of additional income could leave a taxpayer whose income is near the cliff much worse off.

Many phaseouts are indexed for inflation so that the phaseout ranges remain fixed in real terms. Phaseouts that are not adjusted for inflation affect more taxpayers over time, as inflation raises nominal incomes and thus lifts more taxpayers above the phaseout thresholds.

In addition to phaseouts, the tax code also contains phase-ins. For example, a portion of Social Security benefits becomes taxable only when a taxpayer’s income reaches certain thresholds, and the taxable portion increases (up to a maximum of 85 percent) as the amount by which income exceeds those thresholds increases.

WHERE ARE PHASEOUTS MOST COMMON?

Description of phase-in and phaseout parameters by filing status and number of children for Earned Income Tax Credit, Child Tax Credit, Child and Dependent Care Credit.

Phaseouts are most common in three areas of the tax code: family benefits, education provisions, and retirement savings provisions (table 1). The beginning and ending points of the phaseout range determine who is eligible for these credits or deductions. For example, the earned income tax credit (EITC) begins to phase out at income of $19,330 for single parents and at $25,220 for married couples with children, limiting EITC eligibility to low-income families. In contrast, the child tax credit (CTC) begins to phase out at income of $200,000 for single parents and at $400,000 for married couples with children, extending CTC eligibility to high-income families.

Phase-in and phase-out parameters by filing status for AOTC, LLC, education expenses deduction, Coverdell education savings accounts, student loan interest deduction, and education savings bond program.Phase-out parameters for saver's credit, Roth IRA contribution limits, deductible traditional IRA contribution limits by filing status.

PHASEOUTS CAN CREATE MARRIAGE BONUSES AND PENALTIES

Phaseouts can create both marriage bonuses and penalties. A marriage bonus reduces a couple’s combined tax bill compared to what they would pay if they were not married and filed separate returns. For example, in 2020, phaseout of the CTC begins at $400,000 for married taxpayers and $200,000 for all other taxpayers. If one spouse in a couple with a child has $300,000 of income and the other has none, their combined income is under the joint filers’ threshold for phaseout of CTC and they can claim a child tax credit. If they were not married, the higher-income spouse could not claim the CTC because his or her income was too high, and the lower-income spouse could not claim the credit because he or she had no income.

Before the TCJA, married couples faced significant marriage penalties because their phaseout range was less than twice that for single tax filers. Under TCJA, most phaseouts for joint filers are exactly twice that for single filers, so many of the marriage penalties are gone.

However, phaseouts still impose marriage penalties on low-income families, and those penalties are often a larger percentage of income than the marriage penalties caused by phaseouts for higher-income taxpayers.

For example, in 2020, a single mother who earns $18,000 and has one child pays no income tax and receives two refundable credits—a $1,400 CTC and a $3,584 EITC (table 2). (In 2020, a single parent with one child begins paying income tax (before credits) when his or her income exceeds $18,650—the standard deduction for a head of household.) If she marries her partner making $40,000—whose 2020 income tax as a single person would be $3,114—she would lose all her EITC (the couple’s income would cause the credit to phase out completely) but would get more CTC. (In 2020, CTC is worth up to $2,000 per qualifying child. The refundable portion of the credit is limited to $1,400.) Losing the EITC means that the couple would pay $1,644 in income tax when married, compared with receiving a net payment of $1,870 (her $4,984 combined credit minus her partner’s $3,114 tax) if they remained single. That difference is a marriage penalty of $3,514, or 6.1 percent of the couple’s adjusted gross income.

Table contrasting AGI, standard deduction, taxable income, tax before credits, child tax credit, earned income tax credit, and tax net of credits for two individuals filing separately and jointly.


Updated May 2020
Data Sources

Internal Revenue Service. 2020. “Individual Retirement Arrangements (IRAs).” Publication 590-A. Washington, DC: Internal Revenue Service.

———. 2020a. “Child and Dependent Care Expenses.” Publication 503. Washington, DC: Internal Revenue Service.

———. 2020b. “Child Tax Credit and Credit for Other Dependents.” Publication 972. Washington, DC: Internal Revenue Service.

———. 2020c. “Earned Income Credit (EIC).” Publication 596. Washington, DC: Internal Revenue Service.

———. 2020d. “Tax Benefits for Education.” Publication 970. Washington, DC: Internal Revenue Service.

———. 2020e. “Your Federal Income Tax: For Individuals.” Publication 17. Washington, DC: Internal Revenue Service.

Urban-Brookings Tax Policy Center. “Marriage Penalty Calculator.”

Further Reading

Internal Revenue Service. 2019. Revenue Procedure 2019-44. “Inflation Adjustments for Tax year 2020.” 

Gale, William G. 2001. “Tax Simplification: Issues and Options.” Testimony before the House Committee on Ways and Means, Washington, DC, July 17.

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