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The Internal Revenue Service (IRS) estimates that $68 billion of the annual $345 billion gross tax gap for 2001 was due to sole proprietors, who own unincorporated businesses by themselves, underreporting their net income by 57 percent. A key reason for this underreporting is well known. Unlike wage and some investment income, sole proprietors' income is not subject to withholding and only a portion is subject to information reporting to IRS by third parties. GAO was asked to (1) describe the nature and extent of sole proprietor noncompliance, (2) how IRS's enforcement programs address it, and (3) options for reducing it. GAO analyzed IRS's recent random sample study of reporting compliance by individual taxpayers, including sole proprietors.

Based on what IRS examiners could find, most sole proprietors, at least an estimated 61 percent, underreported net business income, but a small proportion of them accounted for the bulk of understated taxes. Both gross income and expenses were misreported. Most of the resulting understated taxes were in relatively small amounts. Half the understatements that IRS examiners could find were less than $903. However, 10 percent of the tax understatements, made by over 1 million sole proprietors, were above $6,200. In this top group, the mean understatement of tax was $18,000. IRS's two main sole proprietor enforcement programs--the Automated Underreporter Program, which computer matches information on a tax return with information submitted to IRS by third parties, and examinations (audits)--have limited reach. The two programs each annually contact less than 3 percent of estimated noncompliant sole proprietors. The limited reach exists for a variety of reasons. In 2001, about 25 percent of sole proprietor gross income was reported on information returns by third parties; expenses generally are not subject to such reporting. Even when required, various barriers make information reporting inconvenient. Examinations of sole proprietors yield less in additional tax assessed and cost more to conduct than examinations for other taxpayers. However, because of the extent of sole proprietor noncompliance, any effect that examinations have on voluntary compliance by other sole proprietors could result in significant revenue. The Treasury Department's recently released tax gap strategy discusses neither sole proprietor noncompliance specifically nor the many options that could address it. GAO has reported on the need for such a detailed strategy for years. Specific options that address issues including sole proprietor recordkeeping, underreporting of gross income, overreporting of expenses, information reporting, and IRS's enforcement programs are listed in appendix II.

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Recommendations for Executive Action

Agency Affected Recommendation Status
Department of the Treasury The Secretary of the Treasury should ensure that the tax gap strategy includes (1) a segment on improving sole proprietor compliance that is coordinated with broader tax gap reduction efforts and (2) specific proposals, such as the options we identified, that constitute an integrated package.
As of May 2021, Treasury has taken no action to address this recommendation and has not provided GAO with plans to do so. Instead, Treasury officials said that the recent Americans' Family Plan Compliance Agenda references compliance options that could affect sole proprietors. The agenda does not reference a strategy including segments on improving sole proprietor compliance. In March 2016, Treasury officials reported to GAO that they have implemented or proposed several actions to address the tax gap among sole proprietors, such as requiring reporting on payment card payments and improved audit selection procedures for sole proprietors. However, GAO's July 2007 report noted many tradeoffs affect various options for improving sole proprietor compliance. GAO recommended that Treasury's strategy for reducing the tax gap include a segment on sole proprietor compliance that is coordinated with broader tax gap reduction efforts.

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