Agency Bonds vs. Treasury Bonds: How Should I Think About the Difference?

Should I Treat Agency Bonds the Same as Treasury Bonds?

Treasury securities and agency securities are often grouped together in fixed-income discussions because of their connection to federal housing, lending, or other public-policy programs. But they are not all obligations of the U.S. government, and the phrase "backed by the government" covers a range of different legal arrangements. Those differences affect credit risk, yield, and state tax treatment in ways that are easy to overlook.

This article walks through what separates a Treasury bond from an agency bond, why the specific guarantee structure, or lack of one, behind each type of issuer matters, and where each type of exposure may fit within a broader fixed-income allocation.

What Is a Treasury Bond?

A Treasury bond, along with Treasury bills and notes, is a direct debt obligation of the United States government, issued by the U.S. Department of the Treasury. Because Treasuries are backed by the full faith and credit of the United States, they are generally treated as the benchmark for very low credit risk in the U.S. bond market.

Key characteristics:

• Direct obligation of the U.S. government, backed by full faith and credit
• Extremely deep and liquid secondary market
• Interest is subject to federal income tax but generally exempt from California and other state income taxes
• Available across a wide range of maturities, from a few weeks to 30 years

What Is an Agency Bond?

"Agency securities" is a broad market term that can include debt issued by certain federal agencies or GSEs, as well as mortgage-backed securities guaranteed, rather than issued, by a government agency or GSE. The two categories are not identical, and the distinction matters:

• Government agencies, such as Ginnie Mae (the Government National Mortgage Association), are government-owned corporations. Ginnie Mae is one such government-owned corporation; it does not issue debt directly but guarantees timely payment of principal and interest on qualifying mortgage-backed securities, a guarantee backed by the full faith and credit of the United States, the same backing behind a Treasury bond.
• Government-sponsored enterprises (GSEs), such as Fannie Mae, Freddie Mac, and the Federal Home Loan Banks, are privately structured entities created by Congress to support specific sectors of the economy, most commonly housing and agricultural credit. None of them carry the same explicit full faith and credit guarantee as a Treasury bond, but the structure behind each one's debt is not identical. Fannie Mae and Freddie Mac have operated under federal conservatorship since 2008, with Treasury financial support provided through Senior Preferred Stock Purchase Agreements; that support does not convert their debt into a direct U.S. Treasury obligation. Their debt has historically been treated by the market as very high credit quality, but it remains legally distinct from a Treasury security.
• The Federal Home Loan Banks are a separate group of GSEs organized differently from Fannie Mae and Freddie Mac. Federal Home Loan Bank debt is not a direct obligation of the U.S. government. The consolidated obligations of the Federal Home Loan Banks are backed by the financial resources of the Banks and are joint and several obligations of the 11 regional Federal Home Loan Banks, not a government guarantee of any kind.

Key characteristics of agency bonds generally:

• Issued to fund a specific public-policy purpose, most often housing or agricultural lending
• Credit quality generally considered very high, though the strength of the guarantee varies by issuer
• Secondary-market liquidity is generally lower than Treasuries, though still substantial for large, frequently issued agency securities
• State income tax treatment varies significantly by issuer, discussed in more detail below

How Do Agency Bonds and Treasury Bonds Compare?

Is Interest From Agency Bonds Exempt From California State Tax?

This is one of the most commonly misunderstood differences between Treasury and agency debt, and it does not follow a single rule across all agency issuers.

Exempt by statute: Interest from Federal Home Loan Bank bonds and from Federal Farm Credit System debt is generally exempt from California and other state income taxes, because the federal statutes creating those entities specifically exempt their interest from state-level taxation, similar to the treatment of Treasury interest.

Generally taxable at the state level: Interest from Fannie Mae and Freddie Mac debt is generally subject to California state income tax. Their charters do not carry the same state tax exemption that applies to Treasuries or to Federal Home Loan Bank debt. Ginnie Mae mortgage-backed securities are typically treated as pass-through interests in pooled mortgage payments rather than a direct government obligation, and are generally subject to state income tax as well, even though the underlying guarantee is explicit and federal.

Why this matters: An investor who assumes all "government" bonds share the same state tax exemption as Treasuries can end up with an unexpected state tax liability, or can misjudge the after-tax yield comparison between a Treasury bond and an agency bond that appears to offer a higher headline rate. Because this treatment depends on the specific issuer and can change with legislation, it is generally worth confirming current treatment with a tax advisor before relying on an assumed exemption.

What Is an Agency Mortgage-Backed Security, and How Is It Different From a Bullet Agency Bond?

Agency debt is not a single structure. "Agency bond" is a broad category that can include fixed-rate, floating-rate, callable, non-callable, discount, and zero-coupon securities, as well as mortgage-backed securities, and the specific structure of a given issue affects its risk profile as much as its issuer does. Federal Home Loan Bank debt alone spans fixed-rate, adjustable-rate, callable, and non-callable bonds. A bullet agency bond is one particular structure within that broader category, and a large portion of the agency market instead consists of mortgage-backed securities (MBS) guaranteed by Ginnie Mae, Fannie Mae, or Freddie Mac, which represent an interest in a pool of underlying residential mortgages rather than a single fixed-schedule obligation.

Non-callable bullet agency bonds:

• Pay a fixed coupon on a fixed schedule
• Return principal at a stated maturity date, similar to a Treasury bond
• Do not carry the mortgage prepayment risk associated with agency MBS

Callable agency bonds:

• Can be redeemed by the issuer before the stated maturity date, typically after a specified call-protection period
• Introduce call risk and reinvestment risk, since an early redemption often occurs when interest rates have fallen and reinvesting the returned principal at a comparable yield becomes harder
• Are a common structure among Federal Home Loan Bank and other GSE issues, not an exception

Agency mortgage-backed securities:

• Cash flows depend on the pace at which homeowners in the underlying pool pay down or refinance their mortgages
• Faster-than-expected prepayments, often triggered by falling interest rates, can return principal earlier than anticipated
• Slower-than-expected prepayments can extend the effective duration of the security beyond what was originally expected
• This dynamic, often called prepayment risk, means the actual timing of cash flows is less predictable than with a non-callable bullet bond of the same stated maturity

This distinction matters when comparing yields across agency securities: an agency MBS, or a callable agency bond, may show a higher stated yield than a non-callable bullet agency bond or a Treasury of similar maturity, but part of that yield can reflect compensation for prepayment risk, call risk, or other structure-specific factors rather than credit risk alone.

Where Might Each Fit in a Portfolio?

Treasury bonds may be considered when:

• High liquidity and a direct U.S. government obligation are priorities
• The bonds will be held in a California taxable account, where the state tax exemption adds to after-tax yield
• An investor wants a benchmark-quality holding against which other fixed-income exposure can be measured

Agency bonds may be considered when:

• An investor is seeking incremental yield over Treasuries while remaining in high-credit-quality government-related debt
• The specific issuer's guarantee structure and state tax treatment have been evaluated and are acceptable for the account in which the bonds will be held
• Exposure to mortgage-related cash flows, including prepayment risk, is appropriate for the investor's time horizon and reinvestment flexibility

A blended approach: Many fixed-income allocations hold both Treasury and agency exposure. The role of each depends on factors such as credit structure, state tax treatment, liquidity needs, and interest-rate exposure. Determining the mix, and confirming which specific agency issuers carry which state tax treatment, is generally best handled as part of a coordinated fixed-income strategy rather than a decision made security by security.

Common Mistakes When Comparing Agency Bonds and Treasury Bonds

Mistake 1: Assuming all agency debt is exempt from California state tax.
Risk: An unexpected state tax bill on Fannie Mae, Freddie Mac, or Ginnie Mae interest that was assumed to be exempt like Treasury interest.
Approach: Confirm state tax treatment issuer by issuer before relying on an assumed exemption.

Mistake 2: Assuming GSE debt carries the same guarantee as a Treasury bond.
Risk: Overestimating the certainty of principal and interest payments on GSE debt during a period of financial stress.
Approach: Recognize that Fannie Mae, Freddie Mac, and the Federal Home Loan Banks are not backed by the same statutory full faith and credit guarantee as Treasury bonds or Ginnie Mae securities, even when day-to-day credit spreads are narrow. Fannie Mae and Freddie Mac rely on federal conservatorship and Treasury support agreements, while Federal Home Loan Bank debt relies on the joint and several financial resources of the Banks themselves.

Mistake 3: Comparing agency MBS yields to Treasury yields without accounting for prepayment risk.
Risk: Selecting an agency MBS based on a higher headline yield without recognizing that part of that yield compensates for uncertain cash-flow timing.
Approach: Evaluate agency MBS yield alongside its effective duration and prepayment sensitivity, not the stated maturity alone.

Mistake 4: Ignoring liquidity differences when sizing a position.
Risk: Assuming an agency bond can be sold as easily and at as tight a spread as a Treasury of the same maturity.
Approach: Recognize that agency debt may have wider bid-ask spreads and lower secondary-market depth than a comparable Treasury, though this varies by issuer and issue size, when sizing individual positions.

Deeper Dives: Related Topics

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The Bottom Line

Treasury securities and agency securities are often grouped together in fixed-income discussions, but they are not all obligations of the U.S. government in the same legal sense, and the state tax treatment that follows from that distinction is not the same either. Treasury bonds carry an explicit federal guarantee, and Ginnie Mae-guaranteed mortgage-backed securities carry an explicit full faith and credit guarantee of the United States for timely payment of principal and interest. Fannie Mae and Freddie Mac debt does not carry that same statutory guarantee and instead relies on federal conservatorship and Treasury support agreements, while Federal Home Loan Bank debt is a joint and several obligation of the Banks, backed by their own financial resources rather than by the U.S. government. California state tax exemption follows a similar, issuer-specific pattern rather than a single blanket rule.

Neither category is a default correct choice. The role of each security depends on factors such as credit structure, liquidity needs, state tax treatment, interest-rate exposure, cash-flow requirements, and account type, and those variables interact in ways that are easy to underweight when comparing headline yields alone.