Municipal bonds, or "Munis," are the "tax shelters" of the fixed income menu. These are bonds issued by states, cities, counties, or other local entities (like school districts or water authorities) to fund public projects like highways, hospitals, and schools . For the investor, the "magic" of Munis is that the interest they pay is usually exempt from federal income tax .

The Triple-Tax-Exempt Advantage

If you live in the same state that issues the bond, the interest is often exempt from state and local taxes as well .

Example: If you live in New York City and buy a bond issued by New York State, you could potentially pay $0 in taxes on that interest at the federal, state, and city levels.
Who benefits most? This advantage is most powerful for investors in high tax brackets. If you are in the 35% or 37% federal tax bracket, a "lower" yield on a Muni might actually put more money in your pocket than a "higher" yield on a taxable corporate bond .

The Two Main Types of Munis

Not all Munis are backed the same way. Understanding the source of repayment is key to assessing risk.

1. General Obligation (GO) Bonds

These are the "safest" Munis. They are backed by the "full faith and credit" of the issuing municipality, which has the power to raise taxes (like property or sales taxes) to pay back the bondholders .

Risk Level: Very low. Defaults are rare because the city can simply increase taxes to cover the debt .

2. Revenue Bonds

These are backed by the earnings of a specific project.

Examples: A toll bridge, a stadium, or a public utility .
Risk Level: Slightly higher than GO bonds. If people stop using the toll bridge, the project might not generate enough revenue to pay the bondholders .
Conduit Bonds: A sub-type where a municipality issues a bond for a private entity (like a non-profit hospital). The private entity is responsible for the debt .

The Math: Tax-Equivalent Yield (TEY)

To compare a tax-free Muni to a taxable bond (like a corporate bond or a Treasury), you have to do a little math. The Tax-Equivalent Yield tells you what a taxable bond would need to pay to equal the Muni's return .

The Formula:
TEY = (Muni Yield) / (1 – Your Tax Rate)

Example:

You are in the 35% tax bracket.
You find a Muni bond yielding 4%.
TEY = 0.04 / (1 – 0.35) = 0.0615 or 6.15%.
The Lesson: You would need to find a taxable bond paying at least 6.15% to beat the "lower" 4% Muni bond .

Risks to Watch For

While Munis are generally safe, they aren't risk-free:

Default Risk: While rare, cities can go bankrupt (e.g., Detroit in 2014 or Puerto Rico in 2018) . Always check the credit rating (AAA is best, BBB- is the lowest "investment grade") .
Call Risk: Many Munis are "callable," meaning the city can pay you back early if interest rates drop (so they can refinance at a lower rate). This leaves you having to reinvest your money at a lower interest rate .
Liquidity Risk: There are over 50,000 different Muni issuers. Some bonds are rarely traded, making them hard to sell quickly at a fair price .

How to Invest in Munis

Individual Bonds: You can buy specific bonds through a broker. This gives you total control but usually requires a larger investment (often $5,000 minimum per bond) to build a diversified "ladder" .
Muni Bond Funds/ETFs: These pool thousands of bonds together. They offer instant diversification and professional management for a low minimum investment (often $100 or less) .
Separately Managed Accounts (SMA): For very wealthy investors (typically $350,000+), a professional manager will build a custom portfolio of individual Munis tailored to your specific state and tax needs .

Summary Checklist for Muni Investors

Check your tax bracket: If you are in a low bracket (e.g., 10% or 12%), Munis probably aren't worth it. Stick to Treasuries .
Check your account type: Never put a tax-exempt Muni bond in an IRA or 401(k). Those accounts are already tax-advantaged, so you are essentially wasting the Muni's biggest benefit while accepting a lower interest rate .
Look for "In-State" bonds: Maximize your tax savings by looking for bonds issued in your home state .
Verify AMT status: Some Muni interest is subject to the Alternative Minimum Tax (AMT). If you are subject to the AMT, look for "AMT-free" bonds .