Where to Park Your Cash: A High Earner's Guide to SGOV, T-Bills, HYSAs, and Munis

Your HYSA Is Costing You Money

If you are a high earner with $50,000+ sitting in a savings account at 4% APY, you are losing hundreds of dollars a year in unnecessary state income taxes. SGOV and direct Treasury bills pay a comparable yield but are exempt from state and local taxes. For a California or New York resident in a high bracket, that difference alone can be worth $500-$1,500 annually on a $100,000 reserve. (Check today’s 3-month Treasury yield before comparing.)

But the yield comparison is only part of the story. Cash is not one monolithic bucket. Money you need this week, this quarter, and next year should not necessarily sit in the same vehicle. This guide covers every major cash storage option for high earners, uses asset-liability duration matching to size and layer your emergency fund, and includes a calculator that recommends where to hold each layer based on your taxes, state, and job risk.

Think in Layers, Not Slogans

"Keep 6 months of expenses in a savings account" is the standard advice. It is not wrong. It is just incomplete. Cash reserves serve different purposes at different time horizons, and the best vehicle for each depends on liquidity needs, tax treatment, and the probability of needing the funds.

Layer 1: Immediate cash (0-1 months). Checking, HYSA, or brokerage settlement fund. You need this money accessible today. FDIC insurance matters here because bank failure risk, however small, is real for operating cash.
Layer 2: Core reserve (2-6 months). The bulk of your emergency fund. You need it within days, not seconds. SGOV, direct T-bills, or a Treasury money market fund. State tax exemption makes this the most tax-efficient layer.
Layer 3: Extended reserve (6-12+ months). For high earners with families, variable income, or layoff risk. Can tolerate slightly less liquidity. Muni money market (if CA/NY), I-bonds as an inflation sidecar, or more T-bills.

This layered approach is rooted in asset-liability duration matching: match the duration of your cash vehicles to the time horizon of each spending need.

How Big Should Your Emergency Fund Be?

The standard 3-6 months guideline is a floor, not a ceiling. For high earners in tech with families and concentrated compensation (RSUs, bonuses), a larger buffer is warranted.

Risk Factor	Additional Months	Why
Base	3	Minimum recommended by most financial planners
Dependents	+1	Higher fixed costs, less flexibility to cut spending
Single income household	+2	No secondary earner to bridge a gap
Tech / layoff-prone industry	+1	Cyclical layoffs, concentrated in one sector
Heavy RSU / bonus compensation	+1	Variable income tied to stock price and retention

A married tech worker with two kids, one income, and significant RSU compensation would target 8 months of essential spending. That is not conservative. That is realistic for a household where a single layoff eliminates 100% of income and a meaningful portion of compensation is locked in unvested equity.

Size Your Reserve and Find Your Best Vehicles

Use the calculator below to size your emergency fund based on your personal risk factors, then see which vehicles give you the best after-tax yield for each layer.

Cash Reserve Optimizer

About You

Monthly Essential Spending$8,000

Dependents

Single Income Household

Tech/Layoff-Prone Field

Heavy RSU/Bonus Comp

Tax Rates

Federal Marginal Rate32%

State Tax Rate0.0%

0% (WA/TX/FL), 5% (CO), 9.3% (CA), 10.9% (NY)

Current Yields

HYSA Yield4.0%

SGOV Yield3.55%

Muni MMF Yield3.2%

Recommended Reserve

$40.0K

3 base + 1 tech field + 1 RSU/bonus = 5 months

Layered Allocation

Immediate

$8,000

1 month in HYSA/checking

Core

$24.0K

3 months in SGOV/T-bills

Extended

$8,000

1 months in SGOV

After-Tax Yield Comparison

Vehicle	Stated	After-Tax	Annual Income	Fit
HYSA	4.00%	2.72%	$1,088	Immediate
SGOV / T-Bills	3.55%	2.41%	$966	Core
Muni MMF	3.20%	3.20%	$1,280	If high state tax

Track your emergency fund coverage on Summitward's dashboard.

How the Calculator Works

The emergency fund target adds months based on risk factors:

\text{Target Months} = 3 + \mathbb{1}_{\text{dependents}} + 2 \cdot \mathbb{1}_{\text{single income}} + \mathbb{1}_{\text{tech field}} + \mathbb{1}_{\text{RSU heavy}}

After-tax yields are computed differently for each vehicle type. For taxable products (HYSA):

y_{\text{after-tax}} = y_{\text{stated}} \times (1 - t_f - t_s)

For Treasury products (SGOV, T-bills), which are state-exempt:

y_{\text{after-tax}} = y_{\text{stated}} \times (1 - t_f)

For tax-exempt municipal money market funds:

y_{\text{after-tax}} \approx y_{\text{stated}}

The SGOV vs. HYSA savings come from the state tax exemption on Treasury income:

\text{Annual Savings} = \text{Reserve Balance} \times y_{\text{SGOV}} \times t_s

Vehicle-by-Vehicle Breakdown

HYSA / Bank Savings

Best for: Layer 1 (immediate cash). FDIC insured up to $250,000 per depositor per bank. Easy to link for bill pay. Weakness: Fully taxable at federal + state rates. No state tax exemption. At a 37% federal + 13.3% CA rate, a 4.0% HYSA yields only 1.99% after tax.

Government Money Market (VMFXX / SPAXX)

Best for: Brokerage settlement, core reserve alternative. VMFXX yielded 3.58% (7-day SEC yield, April 2026); SPAXX yielded 3.29%. Caveat: Not FDIC insured. State tax exemption is only partial: Vanguard reported 66.61% of VMFXX dividends as U.S. government source for 2025; Fidelity reported 50.90% for its Government Money Market class. So you get less state tax benefit than SGOV or direct T-bills.

SGOV (iShares 0-3 Month Treasury Bond ETF)

Best for: Layer 2 (core reserve). 3.55% SEC yield, 0.09 years duration, 0.09% expense ratio, 0.01% bid-ask spread (April 2026). 95.14% of 2025 dividends qualified as U.S. government source income. ETF wrapper means you can buy and sell intraday. My default recommendation for taxable cash reserves.

Direct T-Bills

Best for: Layer 2/3 when you want to match a specific maturity (quarterly taxes, tuition payment). 4-52 week maturities, $100 increments, 100% state-exempt. Buy via TreasuryDirect or brokerage. Drawback: TreasuryDirect is clunky; selling before maturity requires transferring to a broker.

I-Bonds

Best for: Layer 3 (extended reserve, inflation sidecar). Currently 4.03% (0.90% fixed + inflation component, Nov 2025 - Apr 2026). State-exempt, federal tax deferred until redemption. Constraints: $10,000 annual limit, 1-year lockup, 3-month interest penalty if redeemed before 5 years. Not a cash substitute; an inflation-linked sidecar.

BOXX (Alpha Architect 1-3 Month Box Spread ETF)

Best for: Advanced users in high brackets who hold large taxable cash balances for extended periods. Aims to deliver T-bill returns through box spreads. 0.19% expense ratio.Risk: Tax treatment is uncertain. The prospectus acknowledges "lack of clear guidance" for some option transactions, and IRC Section 1258 could recharacterize returns.Not recommended as a default. Use only if you understand and accept the tax uncertainty.

When Munis Beat Treasuries

For high earners in California and New York, municipal money market funds can beat SGOV after tax because muni income is exempt from both federal and state taxes. The tax-equivalent yield formula:

\text{TEY} = \frac{y_{\text{muni}}}{1 - t_f - t_{\text{NIIT}} - t_s - t_{\text{local}}}

Fund	Stated Yield	Tax-Equivalent Yield (CA 37%+13.3%)	Tax-Equivalent Yield (NYC 37%+10.9%+3.9%)
VMSXX (national muni MMF)	3.24%	~6.5%	~6.7%
VCTXX (CA muni MMF)	2.84%	~6.2%	N/A
VYFXX (NY muni MMF)	2.83%	N/A	~6.4%

Yields from Vanguard (April 2026). TEY calculations are approximate and assume top brackets. Muni income is also exempt from NIIT (3.8%).

Important: muni money market funds are not FDIC insured. And the tax exemption does not repeal duration. Munibond funds (VTEB, MUB) with 6-8 year durations are taxable fixed-income holdings, not emergency cash. Keep the distinction clear.

Yields cross over month to month. Sometimes munis win; sometimes Treasuries win. Summitward’s Cash Yield Tracker compares after-tax yields across the curated fund universe with your bracket and lets you override yields with fresh numbers from each fund’s official page.

Who This Is For

High earners with taxable cash reserves who are paying unnecessary state taxes on HYSA interest.
Tech workers with families who need a properly sized emergency fund that accounts for layoff risk, single-income dependence, and RSU concentration.
CA and NY residents where the state tax savings from Treasuries and munis are the largest.
Anyone comfortable using a brokerage account for cash management (SGOV trades like any other ETF).

Who This Is NOT For

People who want everything in one checking account. This strategy requires a brokerage. If you want maximum simplicity, a HYSA is fine.
People in no-income-tax states with small reserves. If you live in WA/TX/FL and have less than $30K in cash, the state tax savings from SGOV vs. HYSA are minimal. A good HYSA is fine.
People who panic at ETF price fluctuations. SGOV's price barely moves, but it does wobble by a few cents around ex-dividend dates. If that causes anxiety, use a money market fund instead.

Frequently Asked Questions

Is SGOV safer than a savings account?

Different kind of safety. A HYSA is FDIC insured against bank failure (up to $250K). SGOV holds U.S. Treasury bonds backed by the full faith and credit of the U.S. government. For amounts above $250K, Treasuries are arguably safer because they do not depend on any individual bank's solvency.

Why is SGOV better than VMFXX or SPAXX for taxable cash?

SGOV is 95%+ U.S. government source income for state tax purposes. VMFXX was only 66.61% and SPAXX's fund family was 50.90% for 2025. So SGOV gives you a cleaner state tax exemption. The yield is comparable.

How many months should a tech worker keep in emergency fund?

6-8 months of essential spending for a dual-income tech household with dependents. 8-10 months if single income. The standard 3-month minimum assumes stable employment and dual income, neither of which is guaranteed in tech.

Should I use I-bonds for my emergency fund?

Only as a supplement, not the core. The 1-year lockup means I-bonds are unavailable when you need them most (a sudden layoff). Use I-bonds for the extended reserve layer, not the first 3-6 months.

Is BOXX worth it?

Only for advanced users who understand box spreads, accept the tax uncertainty (IRC Section 1258 risk), and hold large taxable cash balances for extended periods. For most people, SGOV is simpler, cheaper (0.09% vs. 0.19%), and has clear tax treatment.

What about CDs?

CDs lock up your money for a fixed term with early withdrawal penalties. For emergency reserves, that is a poor match. T-bills offer similar safety with better liquidity and state tax exemption. CDs make sense only for very specific maturity matching (e.g., a known expense in 12 months) and only when the CD rate meaningfully beats T-bill rates.

Key Takeaways

Think in layers, not slogans. Immediate cash (HYSA), core reserve (SGOV/T-bills), extended reserve (munis/I-bonds). Match vehicle duration to spending horizon.
SGOV is an excellent default for taxable reserves. 3.55% yield, 0.09 years duration, 95%+ state-exempt, ETF liquidity. Beats HYSA after tax in every state with income tax.
FDIC is not overrated in general. It solves a real problem for bank deposits. But for Treasury exposure, safety comes from the U.S. government backing, not from FDIC.
High earners in CA/NY should consider muni money markets. Tax-equivalent yields of 6%+ are achievable with VCTXX/VYFXX for appropriate portions of reserves.
Tech workers need more than 3 months. Dependents, single income, layoff risk, and RSU concentration all warrant larger buffers. 6-10 months is reasonable.
The tax exemption does not repeal duration. Muni bond funds (VTEB, MUB) are taxable bond holdings, not emergency cash. Keep the distinction clear.

Related Guides

The RSU Bridge Strategy — why high-earner tech households use a short-duration Treasury reserve bucket to bridge spending between quarterly RSU vests
Emergency Fund Sizing: The Job-Risk Matrix — how much cash to set aside, with a sizing calculator that translates income-shock risk into a recommended range
Can 37% of Americans Really Not Afford a $400 Emergency? the Federal Reserve $400 statistic, what it actually measures, and a liquidity stress test for shocks bigger than $400
The Best Inflation Hedges Are Boring — why I Bonds and TIPS beat HYSA for medium-term purchasing- power protection, with an after-tax real yield calculator
Asset-Liability Matching — the framework for matching cash duration to spending needs
Tax-Aware Decumulation — how cash reserves fit into the broader retirement withdrawal plan
HSA Investing Strategy — another triple-tax-advantaged vehicle for high earners
Roth vs. Traditional — the broader tax-advantaged account hierarchy