Understanding Sub-Sovereign Obligations (SSOs)

Understanding Sub-Sovereign Obligations (SSOs)

3 Min.

Sub-Sovereign Obligations (SSOs) are debt instruments issued by governmental entities beneath the level of the central government, such as states, cities, or provinces, to finance local projects. Municipal bonds are a typical example of an SSO. They are often tax-exempt, making them appealing to high-income investors. SSOs carry risks, including the risk of default and call risk, with callable bonds being subject to potential early redemption by the issuer.


Sub-Sovereign Obligations represent debt securities issued by entities at various levels below a country's central government. These issuers might be states, provinces, municipalities, cities, or towns, engaging in raising funds to finance community-based projects through bond issuance.

The Functionality of SSOs

Entities at sub-sovereign levels undertake these debt obligations primarily to source funds for projects aimed at enhancing the value and services within their jurisdictions. Investors or supervisory governmental bodies can invest in these municipal bonds. They function on the premise of the issuing bodies committing to periodic interest payments and the eventual repayment of the principal upon maturity.

The Tax Advantages of SSOs

The allure of SSOs, especially municipal bonds, often lies in their tax-exempt status. Federal income tax exemption is standard for municipal bonds, with additional state and local tax exemptions available for residents of the state where the bond is issued. This exemption applies to bond funding projects that serve the public interest. However, if the financed projects do not provide clear public benefits, the SSOs will be taxable. Taxable bonds include those issued for pension fund shortfalls, local sports facilities, or investor-led housing.

Special Case: Build America Bonds (BABs)

As a noteworthy example, Build America Bonds are taxable SSOs introduced under the American Recovery and Reinvestment Act of 2009. Despite their taxable nature, they offer special tax credits and federal subsidies for both issuers and holders.

Risks Associated with SSOs

Credit rating agencies assess the risk of default for each SSO issuer, rating the bonds accordingly. Although sub-sovereign entities back these bonds, they tend to have a lower default risk compared to corporate bonds, which is reflected in their lower yield.

Call Risk and Reinvestment Risk

SSO investors must consider call risk—the possibility that an issuer will redeem their bonds before maturity, usually to refinance the debt at a lower interest rate or to restructure payment terms. This action stops interest payments and presents the investor with reinvestment risk, particularly in a declining interest rate environment where new investments may yield lower returns.


Sub-Sovereign Obligations are vital financial instruments for municipal and local entities to fund public-benefiting projects. While offering tax advantages and typically exhibiting lower default risk than corporate bonds, they are not without risks, such as the possibility of being called. Both issuers and investors must weigh these factors carefully to ensure the fiscal health and investment viability of SSOs.

Municipal Bond
Sub-Sovereign Obligation (SSO)