The 50% Rule That Could Quietly Cost AGG Holders a State Tax Break in California, New York and Connecticut

Ask most retirees about Treasury interest, and they will tell you it escapes state income tax. If you own a Treasury note directly, they’re right. If you hold Treasuries through the iShares Core U.S. Aggregate Bond ETF (NYSEARCA:AGG) while living in California, New York, or Connecticut, that exemption can quietly disappear. All three states apply a 50% asset test to fund dividends. On the latest available reading, AGG appears to sit below that line.

A Tiny Fee Hides a Bigger Line Item

AGG sells itself on cost. Its prospectus dated June 29, 2026 lists gross and net expense ratios of 0.03%. That fee barely registers. For some holders, the bigger cost shows up on a state tax return, and no factsheet lists it.

AGG pays a distribution every month. The latest was $0.334142 per share, with an ex-dividend date of October 1, 2026. The 10-year Treasury yielded 4.99% on October 27, so the Treasury piece of that income is real money. Returns leave little room for avoidable tax, too. Over the five years through October 28, 2026, AGG’s dividend-adjusted price fell 1.34%.

Three States Draw the Same 50% Line

Each state lets a fund pass U.S. government interest through tax-free, but only if the fund clears a quarterly asset test:

• California: Under Cal. Rev. & Tax. Code § 17145(a), a fund can pay exempt-interest dividends only if at least 50% of the value of its total assets is in obligations whose interest would be state tax-exempt for an individual. That test applies “at the close of each quarter of its taxable year”.
• New York: N.Y. Tax Law § 612(c)(1) lets shareholders subtract fund dividends designated as U.S. obligation interest only if at least 50% of the fund’s total assets are U.S. obligations at the close of each quarter. The fund must also designate that amount in a written notice to shareholders within sixty days after its taxable year ends.
• Connecticut: Conn. Gen. Stat. § 12-718 allows a fund to pay exempt dividends only if at least 50% of its total assets, measured at the close of each quarter, are obligations that federal law bars Connecticut from taxing.

Each test is a hard threshold. A fund that falls short loses pass-through treatment for its government interest, and residents of these states pay state tax on that interest as ordinary dividend income.

Where AGG Sits on the Line

On October 28, 2026, iShares put Treasuries at 46.76% of AGG’s market value. Mortgage-backed pass-throughs made up another 22.83%. For state tax purposes, agency mortgage bonds generally don’t count as U.S. obligations, so they add nothing toward the 50% threshold. That makes the Treasury weight the number to watch.

That figure comes with a catch. It is a one-day sector breakdown, while the law looks at holdings at each quarter-end, and AGG’s mix changes as its index rebalances. On that date, AGG appeared to sit below the line. Whether it passed or failed in each quarter of its taxable year will show up in the fund’s year-end tax information.

Who Pays and Who Escapes

The cost falls on California, New York, and Connecticut residents who hold AGG in taxable brokerage accounts. Holding AGG in an IRA or 401(k) avoids the issue, because distributions inside those accounts are not taxed by the state when they are paid. Many other states let the Treasury portion pass through regardless of the 50% line. The same fund can deliver a different after-tax yield depending on where its owner lives.

Treasury-Only Funds Can Avoid the Gap

To get the state break on government interest, look at funds built entirely from Treasuries. In its portfolio filing as of July 31, 2026, the iShares U.S. Treasury Bond ETF (CBOE:GOVT) listed debt holdings issued by the United States, with only small short-term cash positions alongside them. The Vanguard Intermediate-Term Treasury ETF (NASDAQ:VGIT) offers similar government-only exposure. Switching has costs of its own. You give up AGG’s corporate bonds and mortgage securities, along with the extra yield and diversification they bring, and Treasury funds still rise and fall as interest rates move.

Check This Before Tax Season

Before you file, pull AGG’s year-end tax information. Look for the percentage of income from U.S. government obligations and whether the fund met the quarterly 50% test. If you live in one of these three states and hold AGG, ask one question: once state tax on the Treasury interest is counted, is a 0.03% fee still the cheapest way to own your core bonds?

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