What Are Private Activity Bonds and How Are Their Proceeds Invested?

A private activity bond is a bond whose issue meets both the private business use test and the private security or payment test, or the private loan financing test, in section 141 of the Internal Revenue Code, and a private activity bond that falls into one of the qualified bond categories in section 141(e) can be tax-exempt.

Its proceeds are invested under the same working framework as any other issue's bond proceeds: the bond documents set the permitted investments, the federal arbitrage rules limit yield and require rebate, and state law adds its own requirements.

This page covers what makes an issue a private activity bond, how the conduit structure works, and what is different about investing and rebate on these issues.

What is a private activity bond?

Under section 141(a), a bond is a private activity bond if its issue meets both the private business use test and the private security or payment test, or if it meets the private loan financing test.

The private business use test is met when more than 10 percent of the issue's proceeds are to be used for private business use, and the private security or payment test uses the same 10 percent threshold.

Section 141(b)(3) adds a 5 percent threshold for private business use that is unrelated or disproportionate to the governmental use.

Private business use means use in a trade or business by a non-governmental person, and section 141(b)(6)(A) leaves use as a member of the general public out of the count.

Tax exemption is not automatic: section 103(a) excludes interest on state and local bonds from gross income, and section 103(b)(1) says that exclusion does not apply to private activity bonds that are not qualified bonds.

Under section 141(e), a private activity bond can still be tax-exempt if it is a qualified bond: an exempt facility bond, a qualified mortgage bond, a qualified veterans' mortgage bond, a qualified small issue bond, a qualified student loan bond, a qualified redevelopment bond or a qualified 501(c)(3) bond.

A qualified bond must also meet the applicable volume cap requirements of section 146 and the requirements of section 147, and IRS Publication 4078 states that qualified private activity bonds generally must use 95 percent or more of net proceeds for the qualified purpose.

Publication 4078 lists the exempt facility categories in section 142, among them airports and spaceports, docks and wharves, mass commuting, water, sewage, solid waste, qualified residential rental, local electric and gas facilities, and qualified highway or surface freight transfer facilities, and it notes that airports, like docks, are not subject to the volume cap.

Whether an issue meets the section 141 tests, and which qualified category it fits, is a determination for bond counsel.

Private activity bonds are one part of a municipal market that SIFMA reported at $4.5 trillion outstanding as of 2Q 2026, up 4.8 percent year over year, with $473.8 billion of issuance through September 2026.

How does the conduit structure work?

In a conduit financing, a governmental issuer issues bonds to finance a project used mainly by a third party, the conduit borrower.

The MSRB glossary is explicit about liability: "the conduit borrower is liable for making debt service payments on the bonds."

The glossary's common types include industrial development bonds, multifamily housing revenue bonds and qualified 501(c)(3) bonds.

The conduit borrower is the main user of the financed project, and the private business use test measures use of bond-financed property by non-governmental persons in a trade or business, so whether a particular conduit issue meets the section 141 tests turns on the facts and is a determination for bond counsel.

How a conduit issuer invests its proceeds is its own question, covered in mGIC's conduit issuer sector guide, and public-private partnership projects have a separate sector guide that covers private activity bond projects.

How are private activity bond proceeds invested, and how does rebate apply?

The mechanics of investing bond proceeds run through the same framework for a private activity issue as for any other: the bond documents set the permitted investments, the federal arbitrage rules limit yield and require rebate, and state law adds its own requirements, with differences covered below.

The proceeds sit in the bond funds the bond documents create, from the project or construction fund to the debt service reserve fund, and each fund's purpose fixes its spending dates and tax limits.

GFOA recommends an investment policy with specific provisions for bond proceeds, provisions that ensure legal and regulatory requirements are met, fair market value bids are received when required by tax law and state or local laws, and issuer objectives are attained.

Where there is no indenture, as with a general obligation bond, GFOA says the policy should list permitted investments, which may be a subset of those for operating funds.

The arbitrage rules apply to private activity bonds as well, with differences, and the stakes are direct: section 103(b)(2) says the interest exclusion in section 103(a) does not apply to any arbitrage bond.

Treasury Regulation §1.148-3(h), with section 148(f)(7), treats a failure to pay the correct rebate on time as making the bonds arbitrage bonds unless the failure was not due to willful neglect and the issuer promptly pays a penalty plus interest.

The penalty is 50 percent for governmental and qualified 501(c)(3) bonds and 100 percent for other bonds, so a private activity bond outside those two categories faces the 100 percent rate.

The regulation provides an automatic waiver where the missed amount plus interest is paid within 180 days of discovery, unless there was willful neglect or the issue is under examination during the window the rule specifies; whether that relief reaches a particular issue is a question for tax counsel.

The small issuer exception draws the private activity line explicitly: under section 148(f)(4)(D)(i), rebate is treated as met for an issue of a governmental unit with general taxing powers if no bond is a private activity bond, 95 percent or more of net proceeds go to the unit's local governmental activities, and the unit reasonably expects to issue no more than $5 million of tax-exempt governmental bonds in the calendar year.

Section 148(f)(4)(D)(vii) raises the $5 million amounts by the lesser of $10 million or the bonds attributable to public school facility construction, which the Instructions for Form 8038-T present as $15 million after 2001, provided no more than $5 million finances non-school purposes, and the statute fixes these amounts rather than indexing them.

mGIC's small issuer exception guide carries the aggregation and refunding rules in section 148(f)(4)(D)(ii) through (vi) and the Treasury Regulation §1.148-8 conditions.

Yield restriction, rebate computation and the spending exceptions each carry their own conditions, covered rule by rule in mGIC's arbitrage guide.

Where does an independent advisor fit on a private activity bond reinvestment?

mGIC (Municipal Government Investors Corp.) is an independent, SEC-registered municipal advisor and Bidding Agent based in Scottsdale, Arizona, that helps issuers structure, competitively bid and close investments of bond proceeds.

The products it evaluates and bids are guaranteed investment contracts, full-flex repurchase agreements and structured portfolios of U.S. Treasury securities, and it sells none of them; mGIC's reinvestment products guide covers each in detail.

mGIC does not act as principal in the investments it evaluates, and its fee is paid by the winning provider rather than the issuer, at or below the safe-harbor maximum in the Treasury arbitrage regulations, with the fee disclosed.

Since mGIC's founding in 2002, its record spans more than $60 billion in bond proceeds invested and swap notional executed across more than 1,000 transactions for issuers in more than 40 states, led by Managing Director Robert Rasmussen.

Its representative reinvestment transactions include Pocahontas Parkway in Virginia, the Grand River Dam Authority in Oklahoma, the DHL air cargo hub at CVG, Miami Air Cargo at MIA, Cardinal Stadium in Louisville, the JFK International Air Cargo Center, Delta Cargo at JFK, aircraft FBOs at Westchester County Airport and Hobby Airport, Birmingham Water Works, Prairie State Energy Campus and OSU Village F student housing.

Each is listed by name, and mGIC's case studies carry the transaction detail.

For a free, no-obligation reinvestment review of a project fund, reserve or escrow, talk to mGIC.

The legal and tax conclusions behind this page, from the section 141 tests to the arbitrage differences, belong to bond counsel and tax counsel.

Last updated 2026-10-06.

This page is general educational information about municipal finance and federal and state rules as of the date shown. It is not legal, tax or investment advice, and it is not a recommendation about any particular investment. Product availability, legality and suitability depend on the issuer, jurisdiction, governing documents and transaction-specific facts. Final legal and tax determinations remain with the issuer's bond counsel, tax counsel and other advisors.