Maturity value
$10,460
Interest earned: $460
Effective APY4.50%
Monthly interest$38
Tax owed (24% bracket)$110
Net after tax$350
Compounding frequency, APY vs APR, and the early-withdrawal penalty everyone forgets about.
A Certificate of Deposit is a time deposit: you give the bank money, the bank gives you a rate, and you both agree you won't touch the money until maturity. The math is straightforward — the levers are how often interest compounds and the early-withdrawal penalty if you break the contract.
A — final amount at maturityP — principal (initial deposit)r — stated annual rate (decimal)n — compounds per year (typically 365 for daily, 12 for monthly, 4 for quarterly, 1 for annual)t — term in yearsThe Truth in Savings Act (12 CFR 1030) requires banks to disclose APY, which folds the compounding frequency into a single comparison number: APY = (1 + r/n)n − 1. Comparing APY apples-to-apples removes the compounding-frequency variable from the shopping decision.
| Time horizon | Best vehicle (typical) |
|---|---|
| 0–3 months | HYSA. Liquidity premium outweighs CD yield pickup. |
| 3–12 months | Short CD or T-bill. T-bill wins in high-state-tax states. |
| 1–3 years | CD ladder, T-notes, or short-duration bond fund. |
| 3–5 years | 5-year CD ladder, I-bonds, or intermediate Treasuries. |
| 5+ years | Equities or longer Treasuries. CDs almost always lose to equities at this horizon. |
CDs preserve purchasing power if you're lucky and lose to inflation if you're not. They have never beaten broad equities over rolling 10+ year periods. Use CDs for known-date cash needs, not for the equity portion of a long-horizon portfolio.
Most CDs auto-renew at maturity into a new CD of the same term — but at whatever the bank's current published rate is, often well below market. You typically have a 7–10 day grace period after maturity to withdraw or move the funds without penalty. Set a calendar reminder for the maturity date.
On a 5-year CD, you owe tax on the credited interest each year — even though you can't withdraw without penalty. The IRS calls it "constructive receipt." Plan for the bill.
Sources: Truth in Savings Act (12 CFR 1030), FDIC Deposit Insurance rules, NCUA Share Insurance, IRS Publication 550 (Investment Income), Federal Reserve H.6 monetary statistics.
APR is the simple annual interest rate before compounding. APY (Annual Percentage Yield) includes the effect of compounding within the year. For deposit accounts the APY is always slightly higher than the APR — at 4.5% APR compounded daily, the APY is 4.60%. Truth in Savings Act (12 CFR 1030) requires banks to disclose APY, not APR, on deposit accounts. Always compare APY when shopping CDs.
Yes. Bank CDs are insured by the FDIC up to $250,000 per depositor, per bank, per ownership category. Credit union "share certificates" have equivalent coverage from the NCUA. To exceed $250k of coverage, split deposits across separate banks or use ownership categories: a single account, joint account, and revocable-trust account at the same bank get separate $250k caps. Brokered CDs purchased through Vanguard, Fidelity, or Schwab pass through to the issuing bank's FDIC coverage.
A CD ladder spreads your principal across CDs with staggered maturities — for example, equal amounts in 1-year, 2-year, 3-year, 4-year, and 5-year CDs. As each rung matures, you reinvest at the new 5-year rate. Benefits: capture longer-term yields without locking everything up, one fifth of your money matures every year (annual liquidity), averages out rate-cycle timing risk.
It depends on the rate cycle. CDs lock a rate for a fixed term; HYSAs float with the Fed. In a falling-rate environment, CDs often win — you keep the high rate while HYSA yields drop. In a rising-rate environment, HYSAs often win because their rate moves up while CDs stay locked. As of late 2025 with the Fed in a cutting cycle, 12-month CDs typically beat HYSAs by 50–100 basis points — the spread compensates you for the lock-up.
Standard CDs charge 3–12 months of interest if you break before maturity. Typical schedule: 90 days for terms ≤ 12 months, 180 days for 13–60 months, 12 months for terms over 5 years. On a 12-month CD held only 6 months, the 3-month penalty can wipe out most or all of the interest earned. Some "no-penalty CDs" allow early withdrawal — at a slightly lower APY.
CD interest is taxed as ordinary income at your marginal federal rate plus state. Form 1099-INT reports the income annually. Critical timing rule: interest is taxed when it's credited to your account, not when you withdraw at maturity. On a 5-year CD that compounds annually, you owe tax each year on the credited interest even though you can't access it without penalty.
A CD purchased through a brokerage (Vanguard, Fidelity, Schwab) rather than directly from a bank. Advantages: comparison shopping across many banks in one place, often higher yields, easy to spread across multiple banks for FDIC coverage. Disadvantages: some are callable (the bank can buy them back if rates fall), they don't compound — they pay simple interest on a schedule, and selling before maturity exposes you to bond-style price risk.
Treasury bills (4-, 8-, 13-, 17-, 26-, 52-week) are the close cousin of short CDs. Two key differences: T-bills are state-tax-exempt federally (CDs are not), meaningful for residents of high-tax states (CA, NY, NJ). T-bills are bought at TreasuryDirect or any brokerage and have a deeper secondary market — easy to sell early without penalty. Yields are typically within 25 basis points of CDs at similar maturities. For taxable accounts in high-tax states, T-bills usually beat CDs after-tax.
Most banks offer 3, 6, 9, 12, 18, 24, 36, 48, and 60 months. Some niche terms exist: 7- and 11-month "odd-month" CDs are common promotional terms. 5-year is the longest traditional bank CD; some brokered CDs go to 10 years. Maturity choice should match your liquidity needs — never buy a CD with money you might need before maturity.
A CD where the issuer (the bank) has the right to buy it back early — typically after 6 months or 1 year — usually when rates have fallen. The headline yield is higher than a non-callable CD to compensate you for accepting the call risk. The trap: if rates fall and the bank calls your CD, you lose the locked-in rate exactly when you most wanted it. Most callable CDs sit in brokerage accounts. Read the prospectus — the "call protection period" tells you how long the bank can't call.