Guides: Treasury income and state tax

Plain-English explainers for investors who know the basics but aren't tax pros. Each one cites the statute, IRS or Treasury page, or issuer document it relies on.

• Are T-bills taxed by states?
  No: Treasury bill interest is exempt from state and local income tax under 31 U.S.C. § 3124 but federally taxable. What that means, with live taxable-equivalent yields.
• T-bill ETFs vs money market funds after state tax
  How much of a T-bill ETF’s or money market fund’s payout is state-tax-exempt, why the share varies by fund, and what it does to your yield.
• The California, Connecticut and New York 50% rule for Treasury funds
  CA, CT and NY exempt Treasury income from funds only if they hold 50%+ U.S. obligations at every quarter-end. How the rule works and which funds met it in 2025.
• SGOV vs a high-yield savings account after tax
  The savings APY you need to match SGOV after state tax in CA, NY, NJ, MA, CT, IL, TX and FL, with SGOV’s live yield and a worked $50,000 example.
• How Treasury bill auctions work (and how to read the results)
  How weekly T-bill auctions work, what the high rate, investment rate and bid-to-cover mean, and a worked example from a recent 13-week auction.