T-bill vs CD vs savings: after-tax yield
- 13-week T-bill4.195%auction Oct 19, 2026
- 3-month CD avg.1.14%FDIC, Oct 19, 2026
- Savings avg.0.38%FDIC, Oct 19, 2026
T-bill interest is exempt from state and local income tax; CD and savings interest generally is not.
Enter a federal bracket and a state rate to see each option's after-tax yield and fully taxable equivalent, using the latest Treasury auctions and FDIC national rates.
T-bills from each term's latest auction (most recent Oct 22, 2026). FDIC national rates and caps published Oct 19, 2026.
After-tax yield calculator
Runs in your browser; nothing you type is sent anywhere. Flat-rate illustration, not personalized advice.
T-bill rates: investment rate at each term's latest auction (U.S. Treasury). CD and savings: FDIC National Rates and Rate Caps, published Oct 19, 2026; the national rate cap is the ceiling that generally applies to banks that are less than well capitalized, not a rate any bank is offering. Ignores the federal deduction for state taxes.
Why state tax matters
Per TreasuryDirect, Treasury bill interest is subject to federal income tax but exempt from state and local income tax (see also 31 U.S.C. 3124). Interest on bank CDs and savings accounts is taxable federally (IRS Publication 550) and generally by states with an income tax. In a state with no income tax, the state column has no effect; the higher the state rate, the wider the gap.
Method
After-tax yield = rate × (1 − tax rate), where the tax rate is federal only for T-bills and federal plus state for CDs and savings. Fully taxable equivalent = after-tax yield ÷ (1 − federal − state). T-bill figures are the investment rate (bond-equivalent yield) from each term's latest auction; CD and savings figures are FDIC national averages and national rate caps. Money market funds are left out because no free official yield source is available.
Related: where to park cash · I bond vs T-bill vs CD · T-bill vs CD tool · T-bill at TreasuryDirect, step by step · Treasury auction results · FDIC national rates.
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Frequently asked questions
Is Treasury bill interest exempt from state income tax?
Yes. TreasuryDirect lists Treasury bill interest as subject to federal income tax but not state or local income tax, and federal law (31 U.S.C. 3124) exempts Treasury obligations from state and local taxation.
Is CD and savings interest taxed by states?
Generally yes. Bank CD and savings interest is taxable federally (IRS Publication 550) and is generally taxable by states that have an income tax.
What is a fully taxable equivalent yield?
It is the rate a fully taxable deposit would need to pay to leave the same after-tax yield. For a T-bill it is the T-bill rate times (1 minus the federal rate), divided by (1 minus the federal and state rates combined). For CDs and savings it equals the stated rate.
Why no money market funds?
There is no free official source of money market fund yields that this site can rebuild and date each week, so they are left out rather than estimated.
Is this personalized advice?
No. It is an educational illustration using flat tax rates. It ignores deductions, the federal deduction for state taxes, local taxes, fees, penalties and compounding. A tax professional can address specifics.