|| Private Activity Bonds
Private Activity Bonds are typically issued by government agencies (City, County, State) to fund civic projects (such as an arena or concert hall). That description may not be 100% inclusive, but is does cover the vast majority of cases.
PAB interest is entered on Form 6251. You get to it by following this path.
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NOTE: Sometimes PAB income will result in the taxpayer owing Alternative Minimum Tax (AMT) shown on Form 6251. If TaxSlayer generates this form in the client's tax return, the return is out of scope (Pub 4012, pg H-1). Refer taxpayer to a paid preparer.