Why T-bill interest skips state income tax
The ranking of cash products changes once state tax hits bank interest but not Treasury interest. The edge is legal structure, not marketing.
Federal vs state layers
At the federal level, the discount you earn on a bill is ordinary interest income in the year of maturity (or as otherwise required). There is no “federal free lunch.”
At the state level, interest on obligations of the United States is widely treated as exempt from state income tax under federal law. That is why a 4.0% bill can beat a 4.5% CD after tax in a high-tax state even though it loses on a pre-tax chart.
A simple ranking example
Suppose federal marginal rate 24% and state 9% on interest. Pre-tax: CD 4.5%, bill 4.0%. After federal only, both shrink. After state, the CD pays another slice on the full 4.5% while the bill’s state slice is modeled as zero in the simple after-tax tool.
Plug your own rates into the comparator. Nine states with no wage tax shrink the edge; California and New York enlarge it. Local city taxes, if any, are not fully modeled — treat them as extra headwind for bank interest.
Broker reporting detail
If Treasury interest is buried in a single 1099-INT box without a Treasury breakout, you may need broker detail or year-end tax documents to subtract correctly on the state return. That operational step is why “state exempt” only helps if you actually claim it.
On this wire
General information, not personalized advice.