Reforming or limiting itemized tax deductions for individuals has gained the interest of policymakers as one way to increase federal tax revenue, increase the share of taxes paid by higher-income tax filers, simplify the tax code, or reduce incentives that might lead to inefficient economic behavior. However, limits on deductions, in the views of some, would have adverse economic effects or changes in the distributional burden of the federal income tax code. Discussions about itemized tax deduction reform are informed by analysis of tax filer data. This report analyzes the most recently available public data from the Internal Revenue Service's (IRS's) Statistics of Income (SOI) to provide an overview of who claims itemized deductions, what they claim them for, and the amount in deductions claimed. In addition, the revenue loss associated with several of the larger deductions is presented using data from the Joint Committee on Taxation's (JCT's) tax expenditure estimates. This report concludes with a brief discussion of the implications of various policy options to reform or limit itemized deductions. More in-depth discussion on options for reforming itemized tax deductions, as a whole or individually, can be found in other CRS reports. Individual income tax filers have the option to claim either a standard deduction or the sum of their itemized deductions on the federal income tax. The standard deduction is a fixed amount, based on filing status, available to all taxpayers. Alternatively, tax filers may claim itemized deductions . Tax filers who itemize must report each item separately on their tax returns and be able to provide documentation in the event of an IRS audit. Whichever deduction a tax filer claims—standard or itemized—the deduction amount is subtracted from adjusted gross income (AGI) to determine taxable income. AGI is the broad measure of income under the federal income tax and is the income measurement before itemized deductions and personal exemptions are taken into account. Generally, only individuals with aggregate itemized deductions greater than the standard deduction would find it worthwhile to itemize. The tax benefit of choosing to itemize is the amount that their itemized deductions exceed the standard deduction multiplied by their top marginal income tax rate. Some itemized deductions can only be claimed if they meet or exceed minimum threshold amounts (also known as a floor) to simplify tax administration and compliance. Floors usually come in the form of a limit based on a percentage of AGI. For example, eligible extraordinary medical and dental expenses must amount to at least 10% of AGI for most tax filers to claim an itemized deduction; total expenses less than this floor are not eligible for an itemized deduction. In addition, some itemized deductions are subject to a cap (also known as a ceiling) in benefits or eligibility. Caps are meant to reduce the extent that tax provisions can distort economic behavior, limit revenue losses, or reduce the availability of the deduction to higher-income tax filers. For example, the itemized deduction for home mortgage interest can only be claimed for the value of interest payments made on the first $1 million of mortgage debt. This section of the report uses publicly available tax data from the IRS to provide a profile of itemizers and some insight into trends among various itemized deduction provisions. Itemized deductions are often grouped together in broader discussions of tax policy, in part because they are grouped together on the tax Form 1040. But, itemized deductions exist for a variety of reasons and are designed in ways such that they target (or exclude) certain types of tax filers. Analysis of data on these deductions can inform these discussions over reforming one or more itemized deduction provisions. Specifically, the data analysis in this report intends to identify who claims itemized deductions, for how much, and for which provisions. This analysis might be relevant to the 115 th Congress, as there has been growing congressional interest in reforming or limiting itemized tax deductions for individuals. Some see reforming itemized tax deductions as one way to increase federal tax revenue (and possibly contribute to deficit reduction), increase the share of taxes paid by higher-income tax filers, simplify the tax code, or reduce incentives that might lead to inefficient economic behavior. In 2014, 30% of all tax filers chose to itemize their deductions rather than claim the standard deduction. Of this 30% of tax filers, a greater share of higher-income individuals chose to itemize their deductions compared with lower-income individuals. Table 1 shows the share of tax filers who chose to itemize their deductions and the average sum of those deductions in 2014 by AGI. Higher-income tax filers chose to itemize their deductions more often than lower-income tax filers in 2014. As shown in Table 1 , the share of tax filers who chose to itemize in income ranges above $200,000 remained virtually the same (over 90%), although the average sum of itemized deductions claimed increases substantially as income rises. For taxpayers with an AGI greater than $200,000, the share that itemized ranged from 91% to 93% and the average sum of itemized deductions claimed per itemizer ranged from $43,131 to $424,864. In contrast, 77% of tax filers with an AGI between $100,000 and $200,000 chose to itemize their deductions in 2014, with an average of $25,598 in deductions claimed. Five percent of tax filers with an AGI less than $20,000 chose to itemize their deductions in 2014, with an average of $15,857 in deductions claimed. Figure 1 shows the distribution, by AGI, of total itemizers and total itemized deduction claimed in 2014. Although higher-income tax filers both tended to itemize at higher rates and claim a larger average total of itemized deductions, the majority of itemizers (56.2%) had incomes less than $100,000, and 86.8% of itemizers had an AGI less than $200,000. Compared with the distribution of itemizers, the distribution of total itemized deduction claim amounts was more even across income ranges. As shown in Figure 1 , a majority (63.6%) of total itemized deduction claims (amounts, in dollars) were made by itemizers with an AGI greater than $100,000. Although tax filers with an AGI more than $1 million comprised 0.8% of itemizers, they claimed 13.1% of all itemized tax deductions in 2014. Similarly, tax filers with an AGI between $500,000 and $1 million accounted for 1.8% of itemizers, but they claimed 5.3% of all itemized deductions. Tax filers with an AGI between $50,000 and $100,000 accounted for 33.6% of all itemizers, but they claimed 23.5% of all itemized deductions. Another way to analyze tax data on itemized deductions is to look at specific deductions. Specific deductions tend to benefit different types of itemizers based on their income. In addition to differences in the income of the itemizer, the variation in itemized deduction claims can also be explained, in part, by the structure of certain provisions (e.g., floors or ceilings that are designed to limit claims). Tax filers in different income ranges tended to claim specific itemized deductions in different frequencies. Table 2 shows the average amount claimed in 2014 for selected deductions and the share of total tax filers who itemized in each income class that claimed a particular deduction. Tax filers in higher-income ranges claimed deductions for charitable gifts, state and local income taxes, and real estate property taxes at higher rates than tax filers in lower-income ranges. For example, the deduction for charitable gifts was claimed by 37% of tax filers with an AGI between $50,000 and $100,000; 68% of tax filers with an AGI between $100,000 and $200,000; and more than 86% of tax filers in each of the income ranges over $200,000. Fewer tax filers in the highest income group (with an AGI greater than $1 million) than in the $100,000-$1 million income groups claimed the home mortgage interest deduction, possibly due to a greater ability for some individuals to pay for home purchases with cash (i.e., they did not have a mortgage). On the other hand, higher-income individuals might have preferred taking a mortgage out on their house, rather than paying in cash, if they believed that their investments would yield a higher rate of return than the cost of the interest on the mortgage. Few tax filers, in general, claimed the deduction for extraordinary medical and dental expenses —particularly at the highest income ranges . The 10% of AGI floor required for most tax filers to claim the deduction in 2014 limited the amount of taxpayers that could be eligible for this provision. Average tax deduction values indicate which provisions had the largest effects in reducing different tax filers' taxable incomes. The mortgage interest deduction was, on average, the largest single deduction, by amount, claimed by tax filers with an AGI less than $500,000 (aside from the medical expenses deduction). In contrast, the deduction for state and local income taxes was the largest average deduction amount claimed for any deduction by tax filers with an AGI greater than $500,000 (aside from the infrequent instance where a tax filer claimed the itemized deduction for extraordinary medical expenses). The average deduction for charitable gifts also increases sharply for tax filers with an AGI of $1 million or above. The average amount of the charitable gift deduction claimed by tax filers with an AGI between $500,000 and $1 million was $18,615. In contrast, the average amount of the charitable gift deduction for tax filers with an AGI greater than $1 million was $172,529 in 2014.