What After-Tax Yield Actually Is — Why the Quoted Rate Is Not the Kept Rate

After-tax yield is the interest rate you actually keep once tax is taken out of what an account pays you. It answers a question the advertised rate cannot: of the yield a bank or fund quotes, how much survives to become money you can spend? For most cash and interest-bearing accounts the quoted rate and the kept rate are meaningfully different, and comparing accounts by the quoted rate alone can rank them in the wrong order.

Why the quoted rate overstates what you keep

Interest from savings accounts, money market funds, certificates of deposit, and most brokerage cash is generally taxed as ordinary income. That means it is added to your other income and taxed at your marginal rate — the rate on your next dollar of income — at the federal level, and in most states at the state level too. The advertised yield is stated before any of that. So an account quoting a given rate hands you that rate minus whatever share your combined marginal tax rate claims. The higher your bracket, the wider the gap between quoted and kept.

The basic arithmetic

After-tax yield is the quoted yield multiplied by one minus your marginal tax rate. If your combined federal and state marginal rate is, for example, one third, then two thirds of the quoted rate survives as after-tax yield. The exact fraction depends on your own bracket and state, which is why after-tax yield is personal: two people looking at the identical account keep different amounts because their tax situations differ. The free After-Tax Yield Calculator does this conversion for each US state so you compare accounts on the kept rate rather than the headline.

Why it changes how accounts rank

After-tax yield matters most when two accounts are taxed differently. Interest from most savings and money market accounts is fully taxable. Interest from US Treasury securities is generally exempt from state income tax, and certain municipal-bond interest may be exempt from federal tax. Because of that, an account with a lower quoted rate can leave you with more after tax than one with a higher quoted rate, once the different tax treatment is applied. Ranking by the advertised number hides this entirely; ranking by after-tax yield surfaces it. That is the whole reason the measure exists.

What after-tax yield does not tell you

After-tax yield is one lens, not a verdict. It says nothing about safety, liquidity, or whether a rate is a temporary teaser. An insured account and an uninsured one can show the same after-tax yield while carrying very different risk. A rate that requires direct deposits or a promotional window may not last. So after-tax yield belongs alongside the questions covered in how a high-yield savings account works — what the insurance covers, how variable the rate is, and what conditions are attached — rather than replacing them.

Where this fits

For a live comparison of high-yield savings, cash, and Treasury venues ranked by what you keep after tax in your state, see the best savings rates table. The Obsidian Metrics community carries the weekly lessons and discussion.

Educational only. Not financial advice. Results not guaranteed. We are not financial advisors. Tax treatment depends on your circumstances; consult a qualified tax professional before acting.