Using Data from the Internal Revenue Service's National Research Program to Identify Potential Opportunities to Reduce the Tax Gap: GAO-07-423R.

The Internal Revenue Service (IRS) most recently estimated that the gross tax gap--the difference between what taxpayers pay in taxes voluntarily and on time and what they should pay under the law--reached $345 billion for tax year 2001. The tax gap arises when taxpayers fail to comply with their individual income, corporate income, employment, estate, or excise tax obligations through (1) underreporting of tax liabilities on tax returns; (2) underpayment of taxes due from filed returns; or (3) nonfiling, which refers to the failure to file a required tax return altogether or on time. IRS's tax gap estimates are based on a variety of data sources. Recently, IRS studied individual taxpayer compliance through the National Research Program (NRP), and used the resulting compliance data to estimate the tax gap for individual income tax underreporting and the portion of employment tax underreporting attributed to self-employment taxes for tax year 2001. NRP, which involved reviewing around 46,000 individual tax returns, has yielded very important new information on taxpayer compliance for the first time since IRS's previous compliance measurement study was undertaken for tax year 1988. Compliance measurement studies such as NRP have the potential to identify ways to improve taxpayer compliance, which could in turn reduce the tax gap and improve the nation's fiscal stability. For example, each 1 percent reduction in the net tax gap would likely yield around $3 billion annually. Given its potential to improve individual taxpayer compliance, you asked us to review the results of the 2001 NRP study. In response, we agreed to identify (1) specific areas of individual taxpayer noncompliance that are promising targets for additional research to improve reporting compliance, and (2) opportunities, if any, found through the course of our work to improve future NRP studies. Areas of individual taxpayer noncompliance that are promising targets for additional research to improve reporting compliance include: income/losses from partnerships and S corporations, income/losses from rental real estate, sole proprietor income/losses, income/losses from farming, other income--net operating losses, gambling income/losses, capital gains for assets other than securities, other gains/losses, Earned Income Tax Credit, Additional Child Tax Credit, deduction for charitable contributions, deduction for medical and dental expenses, deduction for job expenses and most other deductions, and exemptions. IRS could benefit from electronically capturing complete NRP examination case files. Although IRS creates an electronic record for each tax return reviewed for NRP, these records do not contain all of the information contained in the corresponding hard copy examination case files. For example, information taxpayers provide to IRS during examinations is only included in the paper case file and not in the electronic records. Furthermore, some paper case files are not... [ABSTRACT FROM AUTHOR]