The Joint Committee staff is nonpartisan and serves the entire Congress. The Congressional Budget Act of 1974 ("the Budget Act"), as amended, stipulates that revenue estimates provided by the Joint Committee staff will be the official estimates for all tax legislation considered by the Congress. The objective of the estimating process is to produce accurate, consistent, fair, and impartial estimates that can be relied upon by Members of Congress in making legislative decisions.
Any Member of Congress may request a revenue estimate for a tax proposal or solicit the Committee staff's help in crafting legislation. In 2005, the Joint Committee staff received 6,054 requests. In 2022, this figure was 2,328. The largest number of requests to date, 8,612, was received in 2013. Since 2013, the number of requests has varied between approximately 2,000 and 7,000 requests. While the majority of requests are for revenue estimates, the Joint Committee staff also receives requests for distributional, legal, and data analyses. All requests are treated as confidential. Responses to requests are provided only to the Member making the request and the response remains confidential unless the Member decides to make the information public. Further, the Joint Committee staff does not acknowledge whether or not a request has been received or provided. Confidentiality allows the Joint Committee staff to maintain its nonpartisan role in the legislative process.
When a revenue estimate is included in a publicly available document (e.g., a revenue table summarizing a markup proposal or the result of a reported bill), the estimate is posted to the Joint Committee website. An estimate is also publicly released in circumstances where the information is of widespread and immediate interest by the Members of Congress (e.g., a tax bill about to be voted upon by the full House or the full Senate).
The starting point for a revenue estimate prepared by the Joint Committee staff is the Congressional Budget Office ("CBO") 10-year projection of Federal receipts, referred to as the "revenue baseline." The revenue baseline serves as the benchmark for measuring the effects of proposed tax law changes. The baseline assumes that present law remains unchanged during the 10-year budget period. Thus, the revenue baseline is an estimate of the Federal revenues that will be collected over the next 10 years in the absence of statutory changes.
In providing conventional estimates, the Joint Committee staff assumes that a proposal will not change total income; it therefore holds Gross National Product ("GNP") fixed. The use of fixed economic assumptions does not prevent the Joint Committee staff from including possible shifts in economic activity across sectors or markets and/or changes in the timing of such activity in response to the proposed tax change, so long as GNP remains unaffected.
The Joint Committee staff uses confidential tax return information to prepare revenue estimates. The Statistics of Income Division ("SOI") of the IRS provides large micro-level data sets consisting of carefully sampled and edited tax returns. SOI data provide the primary building block for revenue estimates. In the process of estimating a proposal, other information sources are used frequently. These sources include other government data, survey data, constituent data, and third-party data.
The Joint Committee staff is required by the budget resolutions to present revenue estimates as point estimates (that is, present one dollar figure rather than a range of possibilities) calculated in nominal dollars. The current budget process also requires the Joint Committee staff to generate revenue estimates of tax legislative proposals over a 10-year period, often referred to as the "budget window." Revenue estimates for each year within the budget window are fiscal year estimates.
Although conventional revenue estimates are sometimes referred to as "static," Joint Committee staff revenue estimates include taxpayers' likely behavioral responses to proposed changes in tax law. Behavioral effects can be broadly characterized as shifts in the timing of transactions and income recognition, shifts between business sectors and entity form, shifts in portfolio holdings, shifts in consumption, shifts in labor supply, and tax planning and avoidance strategies. See Revenue Estimating Process January 2023 and JCX-46-11 for a few specific examples that give a flavor for the issues the Joint Committee staff considers when accounting for behavioral effects in revenue estimates.
The Joint Committee staff attorneys, accountants, and economists working as a team examine compliance, administration, and enforcement issues that could affect the timing or amounts of revenues collected as part of the process of understanding how a proposal would operate. When these issues are likely to be important to a proposal, the Joint Committee staff accounts for their effects in the revenue estimate.
The Joint Committee staff uses a variety of sources to determine how compliance, administration, and enforcement issues might affect revenue. IRS compliance studies provide information for issues involving individual taxpayers. The Joint Committee staff also uses information provided by the IRS about their examination, enforcement, appeal, and litigation activities. In some areas, such as tax shelters, the Joint Committee staff is frequently briefed by IRS personnel. Information provided at these meetings helps the Joint Committee staff gauge the likely compliance, administrative, and enforcement effects of particular proposals.
In estimating the revenue effects of proposed changes to tax law, the Joint Committee staff incorporates the behavioral responses of taxpayers (within the fixed-GNP convention) and any indirect tax effects associated with that behavior. These secondary effects are not the direct result of tax changes. Instead, they arise from changes in taxable income induced by behavioral responses to tax changes. For example, for a policy that adds employer provided health insurance benefits to taxable wages, Joint Committee staff estimate increased revenue from directly taxing those benefits, but Joint Committee staff would also estimate (in addition to other behavioral effects) the indirect effect this policy has on the mix of compensation. In particular, adding health benefits to taxable wages will increase the employer’s contribution for Social Security. Because Joint Committee staff hold overall compensation fixed, that increase in payment cannot result in an increase in overall compensation, thus the Joint Committee staff assumes that take-home wages decline.
Indirect tax effects are not limited to changes in tax law, however. Non-tax legislation, either by design or not, may cause changes in taxable income and thereby impact Federal tax receipts. The CBO has responsibility for estimating the budget effects of non-tax legislation, and over time CBO has developed general guidelines for when indirect tax effects are included and by whom (often in consultation with the Joint Committee staff). Regardless of whether CBO or the Joint Committee staff estimates the indirect tax effects, to the extent that these effects are accounted for they are included with the estimate of the bill.
In estimating the revenue effects of changes in excise taxes, the Joint Committee staff (along with staff at CBO and Treasury's Office of Tax Analysis) generally assumes that the net effect on total Federal tax receipts from an increase in Federal excise taxes is less than the increase in gross excise tax receipts. The difference between the change in excise tax receipts and the change in total Federal tax receipts is referred to as the "income and payroll tax offset." The difference arises from the fact that an increase (decrease) in excise taxes results in a decrease (increase) in income subject to Federal income and payroll taxation. The existence of the income and payroll tax offset for excise taxes has become an established, generally accepted component of revenue estimates for excise taxes. In addition to the offset for excise taxes, the Joint Committee staff (along with staff at CBO and Treasury's Office of Tax Analysis) incorporates an income and payroll tax offset when estimating the effects of changes in payroll taxes. The Joint Committee staff updates their estimate of the income and payroll tax offset annually and posts it to the website www.jct.gov. See JCX-59-11 for a more detailed discussion of the mechanics of the income and payroll tax offset and how the Committee staff estimates it.
Distributional analysis—that is, analyzing the effects of tax law changes across the income distribution—is not a legally required task of the Joint Committee staff. However, upon request of Members or committee staff, distributions of certain tax changes are provided as background information. The Joint Committee staff has produced distributional analyses since the 1940s, see JCT-18-11. The current distribution methodology dates to 1994 with significant revisions in 2013 to the distribution of business income, see JCX-14-13. Under the distribution methodology, the Joint Committee staff provides a distribution by current income group, when sufficient information is available, for legislation affecting the individual income tax, corporate income tax, Social Security and Medicare payroll taxes, and excise taxes. The current methodology does not distribute estate and gift taxes.
The measure used in the distributional analysis is the change in liability (taxes paid) for the taxable year. Liability is measured, whenever possible, after any behavioral response related to the tax change. Compliance issues are also included in the measurement of liability.
The basic unit of analysis is the tax filing unit or return. Changes in tax liability are distributed to taxpayers according to their expanded income. This income classifier begins with Federal adjusted gross income and adds tax-exempt interest, employer contributions for life and health insurance, employer share of Social Security and Medicare payroll tax, workers' compensation, untaxed Social Security benefits, insurance value of Medicare benefits, alternative minimum tax preference items, and excluded income of U.S. citizens living abroad. Yearly distributions in nominal dollars are provided for the first five years of the 10-year budget window.
The Joint Committee staff uses several highly developed microsimulation tax models to estimate the revenue impact of changes in tax laws. These are the Individual Model, the Corporate Model, the International Cross Border Model, and the Estate and Gift Model. In addition, the staff uses panel-based models and data for both individuals and business entities. The primary source of tax data for the models comes from the SOI division within the IRS. Some of the models use large micro-data files, while others are smaller and spreadsheet based. Some models reside on a desktop computer, while others reside on "servers" and are simultaneously available to several staff members. With respect to any revenue estimate, the complexity and scope of the model used are determined by several factors including the amount and type of data available, the level of interest in the model, and the level of complexity associated with the questions being asked of the model.
From time-to-time tax legislation as enacted may not exactly reflect the intent of the legislators. When this occurs, legislators may seek a technical correction to fix the statutory language. The Joint Committee staff does not provide estimates of the revenue effect of technical corrections. This convention stems from the view that the original revenue estimate reflects the intent of the legislation. Therefore, an estimate of the correcting provision would be a double counting of the effect of the original policy.
An overview of the current procedures used in the revenue estimating process is provided in Joint Committee on Taxation, Summary of Economic Models and Estimating Practices of the staff of the Joint Committee on Taxation, (JCX-46-11), September 19, 2011. The report provides a summary of the revenue estimating responsibilities of the Joint Committee staff; discusses requirements, constraints, and conventions of the revenue estimating process; and presents the estimating procedures and models used by the Joint Committee staff in preparing revenue estimates. The emphasis is solely on methodology and issues associated with the preparation of conventional revenue estimates of proposed changes to the Internal Revenue Code.
In addition to estimating the revenue effects of proposed tax legislation, the Joint Committee staff also analyzes the macroeconomic effects of certain tax legislation, in compliance with a series of House and Senate rules dating back to 2003. The Joint Committee staff has provided macroeconomic analyses both in compliance with these rules and in response to confidential requests. There are a number of relevant documents under the “Macroeconomics” heading in Publications of this website, for example Macroeconomic Analysis Of The Conference Agreement For H.R. 1, The Tax Cuts And Jobs Act (JCX-69-17), December 22, 2017; and Macroeconomic Analysis At The Joint Committee On Taxation And The Mechanics Of Its Implementation, (JCX-3-15), January 26, 2015.