Where to Park Your Cash: HYSA, T-bills, I-bonds, and CDs

7 min read

Personal Finance Basics

Most people park their cash in a checking or traditional savings account earning 0.01% to 0.50% — and quietly lose hundreds or thousands of dollars a year to an invisible cost: the difference between that rate and what safe, liquid alternatives pay. If you're holding more than a month or two of expenses, you have real options. This guide covers the four main places to park cash and when each makes sense.

The Four Options at a Glance

Vehicle	Typical Yield	Liquidity	Insurance	Tax Treatment
High-yield savings (HYSA)	~4–5%	1–2 business days	FDIC up to $250k	Fully taxable
Treasury bills	~4–5%	Sell anytime, T+1	Full faith of US gov	State-tax-exempt
I-bonds	Inflation-linked, variable	1-year lock, 5-yr penalty	Full faith of US gov	Fed-deferred, state-exempt
CDs	Fixed rate, term	Locked to maturity	FDIC up to $250k	Fully taxable

High-Yield Savings Accounts (HYSA)

A savings account at an online bank or credit union paying far more than a brick-and-mortar bank. This is the right default for most people's emergency funds and short-term savings.

Best for: Emergency funds, savings goals within 12 months, and money you might need within a week.

Why: FDIC insured, highly liquid (same-day or next-day transfers), no lockup, and rates that track the market. The main drawback is that the rate floats — when the Fed cuts, HYSA yields fall too. You can't lock in a rate.

Treasury Bills (T-bills)

Short-term US government debt you buy at a discount and redeem at face value. Terms range from 4 weeks to 52 weeks. You can buy them directly from the government or through a brokerage.

Best for: Savers in high-tax states, larger cash balances, and anyone who wants the safest possible yield with a meaningful tax advantage.

Why: T-bill interest is exempt from state and local income tax, which in a high-tax state (CA, NY, NJ) is worth 0.3–0.5% of effective yield. They're backed by the full faith of the US government, can be sold anytime before maturity, and are easy to ladder. The tradeoffs: buying direct requires setting up a TreasuryDirect account, and you have to manage maturities yourself rather than getting a simple APY.

I-bonds (Series I Savings Bonds)

US savings bonds whose rate has a fixed component plus an inflation component that resets every six months. They're designed to protect purchasing power.

Best for: Long-term cash you won't need for at least a year and want protected from inflation.

Why: I-bonds are guaranteed to at least keep pace with inflation, interest is deferred until you redeem, and like T-bills they're exempt from state tax (and can be fully tax-free if used for qualified education expenses). The tradeoffs: your money is locked for the first 12 months, you forfeit the last 3 months of interest if you redeem before 5 years, and there's a $10,000 annual purchase limit per person. They're a savings tool, not a place for money you need soon.

Certificates of Deposit (CDs)

A bank deposit that locks up money for a fixed term (3 months to 5+ years) in exchange for a guaranteed rate.

Best for: Cash you definitively won't need until a known future date, and when you believe rates are peaking and want to lock in.

Why: The rate is locked, FDIC insured, and known up front. The tradeoffs are meaningful: early withdrawal penalties, no access during the term, and the risk that rates rise after you lock in a lower one.

How to Decide: Match the Vehicle to the Goal

Situation	Best Choice
Emergency fund	HYSA — liquidity beats yield.
Saving for a house in under a year	HYSA or a money market fund — short horizon, prioritize convenience.
High state-tax bracket, large cash balance	T-bills — the state-tax exemption is real money.
Cash you won't touch for 2+ years, want inflation protection	I-bonds (respecting the $10k limit and 1-year lock).
Known expense on a fixed future date, rates likely peaking	CD matched to that date, or a CD ladder.

The Laddering Pattern

If you have a large cash balance and want both yield and regular access, build a ladder: split the money across maturities so a portion is always coming due. With T-bills, buy 4-week, 8-week, 13-week, and 26-week maturities and reinvest each as it matures. With CDs, split across 3, 6, 9, and 12-month terms. You get most of the yield of locking up money while keeping a steady stream of liquidity.

The Bottom Line

The single highest-leverage move most people can make is simple: move idle cash out of a 0.01% account and into a high-yield savings account. On a $10,000 balance, the difference between 0.01% and 4.5% is roughly $450 a year — for doing almost nothing. From there, T-bills and I-bonds add tax advantages for specific situations, and CDs are a precision tool for known future dates. Match the vehicle to the goal, not to the headline rate.