Fidelity Cash Management Account: Can SPAXX Replace Your Checking Account?

Rates move. Fund yields and the sweep rate are Fidelity’s for October 6, 2026; returns run to September 30, 2026; the checking average is the FDIC’s September 21, 2026 posting.

Most households keep their spending money in an account that pays close to nothing, and park anything that earns a market rate one transfer away. The CMA removes that step. The balance you spend from is the balance that earns. That leaves two questions: how close SPAXX actually gets to the rate on Treasury bills, and what you give up to get it.

How the Cash Management Account works

Fidelity describes the CMA as “a brokerage account designed for spending and cash management.” It has no minimum balance and no account fee, a routing and account number for direct deposit, free checks and bill pay, mobile check deposit and free wires.¹ The debit card charges no foreign transaction fee, and Fidelity reimburses ATM fees at any machine showing the Visa, Plus or Star logo, crediting the refund the same day.¹

Money that arrives goes into the account’s core position. In a CMA there are two choices: SPAXX or the FDIC-Insured Deposit Sweep.² When a debit card charge, check or bill payment comes through, Fidelity pays it in a fixed order: intraday free credit first, then the core, then any Fidelity money market fund in the account that holds a $1.00 price and is not charging a liquidity fee, then margin if you have it.³ Fidelity’s “Cash Available to Withdraw” balance counts the core and those other money funds, and leaves out deposits that have not cleared.⁴ The core choice itself, and the case for SPAXX over the sweep in most accounts, are covered in Best Fidelity Core Position.

One recent change: for a CMA opened on or after September 28, 2026, “available investments are limited to fixed income products, such as bonds and CDs, and Fidelity money market mutual funds.”¹ The limit is written for accounts opened on or after that date. Stocks and ETFs now belong in a regular brokerage account, which can sit alongside the CMA under the same login.

What each option paid in October 2026

Sources: FDIC national rates; Fidelity CMA rate page and fund pages; Treasury daily bill rates.⁵⁶⁷⁸⁹

The FDIC figure is an average for interest-bearing checking accounts with a $2,500 balance, and plenty of checking accounts pay nothing.⁵ The money fund yields are already net of their 0.42% expense ratios.⁷ Bills sat above the fund yields partly because the Federal Reserve raised its target range to 3.75% to 4.00% on September 16, 2026, and bills reprice faster than a fund’s 7-day average.¹⁰

How much this is worth depends on how much you keep in checking. The Federal Reserve’s 2022 Survey of Consumer Finances put the median balance in transaction accounts (checking, savings, money market and call accounts), among families that had them, at $8,000.¹¹ On $8,000, the gap between 0.07% and SPAXX’s October 6 yield comes to about $270 a year before tax. On $25,000 it is about $855. Measured in time, the JPMorgan Chase Institute found that from 2009 to 2020 the median household kept 13 to 26 days of spending in checking and savings, depending on income.¹²

Checking against SPAXX at your tax rates

Type in what your checking account pays. In California, Connecticut and New York the calculator taxes all of SPAXX’s income, as those states do (see the tax section below).

How close SPAXX gets to Treasury bills

Fidelity benchmarks SPAXX against the FTSE 3-Month Treasury Bill index. In every calendar year since 2022, and over every trailing period it publishes, the fund returned less.⁷

Source: Fidelity, SPAXX performance page, as of September 30, 2026. Gaps are in percentage points.⁷

In rate-heavy years the gap has run close to half a point. The expense ratio accounts for most of it: add the 0.42% back to SPAXX’s 3.49% yield and the fund earned about 3.91% gross on October 6, against 4.14% for a 13-week bill that day. The rest comes from what the fund holds. On September 30, 2026, SPAXX had 42.5% in Treasury securities, 27.2% in agency debt (most of it floating-rate) and 32.7% in repurchase agreements backed by government securities, net of a small negative cash line.⁷ Repo and floating-rate agency notes reset with overnight rates, which sat below the 3-month bill yield in October. The fund must hold at least 99.5% of assets in cash, government securities or fully collateralized repo.⁷

What the convenience costs against bills

This calculator puts both sides on the same basis, the one-year return to September 30, 2026, and applies state tax. Bills win by more in a high-tax state, because Treasury interest is exempt from state income tax and, in California, Connecticut and New York, none of SPAXX’s income is.

At a 0.47-point gap the trade is about $10 a month per $25,000 before tax. Buying bills directly means bidding at auction or in the secondary market, rolling them as they mature, and selling them to move money back to spending cash. Most people would not do that for $10 a month on their bill-paying balance. On a $200,000 cash reserve that will sit for a year, the same gap is worth about $940 a year before tax, and the work is more likely to be worth it. SGOV vs. T-Bills covers the mechanics.

Why checking accounts pay so little

For most of the last century banks were not allowed to compete for checking balances on rate. The Banking Act of 1933 banned interest on demand deposits and let the Federal Reserve cap rates on savings accounts. The caps were phased out by 1986, and the ban on interest on demand deposits was not repealed until 2011.¹³ Money market funds appeared in the early 1970s, while the caps were still in force.¹⁴ In 1977 Merrill Lynch launched the first Cash Management Account: a brokerage account tied to a money market fund, with check writing and a Visa card issued through Bank One.¹⁵ Fidelity’s CMA is a modern version of the same design.

The cost of holding cash

The textbook model of why people hold low-yielding cash comes from William Baumol in 1952 and James Tobin in 1956.¹⁶¹⁷ A household that spends T a year, pays a fixed cost b each time it moves money out of an interest-bearing asset, and gives up interest i on whatever sits in cash, minimizes its total cost by holding an average cash balance of √(bT/2i). Two forces set the answer. The more each transfer costs, the more cash you keep idle; the more interest cash gives up, the less you keep.

A CMA with a money market core changes the second term. Your transaction balance now forgoes the gap between SPAXX and bills, about half a point over the past year, instead of the gap between checking and bills, which was close to four points. Merton Miller and Daniel Orr extended the model in 1966 to cash flows that arrive at random. Their answer is a buffer with an upper and a lower limit, topped up or drawn down when the balance hits either one.¹⁸ A buffer that earns close to the market rate costs very little to hold, which is why a CMA user can keep a larger one without paying much for it.

Banks know most depositors will not move

Banks pass rate increases through to depositors slowly. In the “deposits channel” paper, Itamar Drechsler, Alexi Savov and Philipp Schnabl found that a one-point rise in the federal funds rate widened the gap between market rates and what large banks paid depositors by about 61 basis points, and that the effect was larger in less competitive local markets.¹⁹ New York Fed economists estimated that from 2010 to 2023 rates on 3-month retail CDs moved 0.08 points for each point of fed funds, while retail money market fund yields moved 0.89.²⁰ That study measured CDs only. Checking moved less still: the FDIC average was 0.07% in September 2026, with bills above 4%. More on bank deposit rates is in Do T-Bills Beat Inflation?

Inattention is part of the business model. An NBER working paper by Mark Egan and coauthors found that only 17% of account closures were switches to a better offer, and estimated that about 58% of bank deposit profits came from depositors not paying attention to rates.²¹ A CMA gets those depositors a market rate without asking them to keep watching it, because the fund’s yield follows short-term rates on its own.

Risks and drawbacks

SPAXX is not FDIC insured

A money market fund is a security, so FDIC insurance does not apply.²² SIPC covers money market fund shares as securities, up to $500,000 per customer, if Fidelity itself fails and your shares are missing. It does not cover a fall in the fund’s value.²³ If you want a government guarantee on the balance itself, pick the FDIC-Insured Deposit Sweep as the core. Fidelity spreads sweep cash across program banks at $245,000 each, says it covers up to $4 million, and places anything above that in a money fund that is not FDIC insured.¹²⁴ Over $250,000 at any one bank, counting what you already hold there, is not covered.

How often money funds break the buck

In September 2008 the Reserve Primary Fund wrote its Lehman Brothers debt to zero and its share price fell to $0.97.²⁵ That was a prime fund holding corporate debt. In 1994 a small institutional government fund, Community Bankers U.S. Government Fund, also fell below $1.00.¹⁴ In the March 2020 panic investors pulled $134 billion from prime and tax-exempt money funds and put $838 billion into government funds.²⁶

Rules adopted in 2023 require money market funds to hold at least 25% of assets in daily liquid assets and 50% in weekly liquid assets, and the liquidity fees in those rules apply to institutional prime and other non-government funds.²⁷ On September 30, 2026, SPAXX held 59% in daily and 75% in weekly liquid assets.⁷ The remaining risk is a large loss on government securities or repo collateral.

State tax in three states

Interest on Treasury securities is exempt from state and local income tax.²⁸ Only part of SPAXX’s income qualifies: 50.90% in 2025, and Fidelity marks the fund as having failed the holdings test that California, Connecticut and New York require.²⁹ Residents of those states pay state tax on all of it. FDLXX, the Treasury Only fund, earned 98.67% of its 2025 income from government securities and passed.²⁹ It cannot be the CMA’s core, but it can be held in the account, and Fidelity sells it automatically to cover debits when the core runs out.³ FDLXX vs. SPAXX works out when that is worth doing.

The yield floats

SPAXX’s yield follows short-term rates in both directions. A 13-week bill locks in its rate until it matures; SPAXX’s 3.49% can be lower next month. For money set aside for a payment due on a known date, a bill maturing just before that date removes the risk. For spending cash that turns over every few weeks, the floating rate makes little difference.

Deposit holds

Fidelity’s CMA agreement says money deposited by electronic transfer is “normally not available for withdrawal for four to six business days.”³ If you fund the account by pulling money from a bank, plan for the hold.

One login for everything

Putting your paycheck, bills, debit card, emergency fund and investments at one firm means a single fraud review, account restriction or outage can freeze all of it at once. Keep a checking account at a bank with a few weeks of spending in it, and a card that draws on that bank.

Spendable money gets spent

A higher yield on spending cash does not tell you how much cash to hold. A balance that earns 3.5% can still be too big for someone with decades to invest, or too small to cover a job loss. Emergency fund sizing covers that question.

When something else fits better

• You want deposit insurance on every dollar. Use the CMA with the FDIC sweep as core, at 1.96% APY on October 6, 2026, or a bank.
• You have a large sum for a known date. A Treasury bill maturing just before the date locks the rate and pays the full bill yield.
• You live in California, Connecticut or New York and hold a large balance. Keep a small SPAXX core for spending and hold the rest in FDLXX or Treasury bills.
• You rely on features this guide could not confirm. Fidelity’s CMA pages do not mention Zelle, cash deposits or early direct deposit. Check with Fidelity before you move a paycheck.

Key takeaways

• The CMA is a brokerage account that works like checking. With SPAXX as core, the balance you spend from earned 3.49% on October 6, 2026, against a 0.07% national average for interest checking.
• SPAXX gets close to bills and stays below them. It trailed a 3-month bill index by 0.19 to 0.53 points in each year from 2022 to 2025, and by 0.47 in the year to September 30, 2026.
• The gap is mostly the 0.42% expense ratio; the rest comes from repo and floating-rate agency holdings.
• SPAXX has no FDIC insurance and no state tax break in CA, CT or NY. The FDIC sweep core and FDLXX address each one, at a lower yield for the sweep.
• Decide how much cash you need first. The CMA only changes what that cash earns.

How Summitward helps

Frequently asked questions

Is the Fidelity Cash Management Account a bank account?

No. It is a brokerage account. Fidelity is not a bank, and the money in it is either shares of a money market fund (SPAXX) or deposits that Fidelity places at program banks (the FDIC sweep), depending on the core you choose.

Does SPAXX pay Treasury bill rates?

Close to them. Over the year to September 30, 2026 SPAXX returned 3.44% against 3.91% for the FTSE 3-month Treasury bill index, and it has trailed that index in every year since 2022. Its 0.42% expense ratio accounts for most of the gap.

Is my CMA cash safe if Fidelity fails?

SIPC protects SPAXX shares as securities, up to $500,000 including $250,000 of cash, if a failed Fidelity cannot return them. Sweep deposits are FDIC insured at the program banks up to $250,000 per bank. Neither covers a loss in the fund’s own value.

Can I use FDLXX in a Cash Management Account?

You can hold it, but not as the core. The core is SPAXX or the FDIC sweep. Fidelity sells other $1.00 Fidelity money funds in the account, including FDLXX, to cover debits once the core is used up.

What changed for CMAs opened after September 28, 2026?

New CMAs can hold only fixed income, such as bonds and CDs, and Fidelity money market funds. Stocks and ETFs go in a separate brokerage account. Fidelity’s wording applies the limit to accounts opened on or after that date.

Should I close my bank checking account?

Keep one. A second account at a bank with a few weeks of spending protects you if the Fidelity account is locked or a deposit is on hold, and it costs little if it stays small.

Related guides

• Best Fidelity Core Position: SPAXX against FZFXX, FCASH and the FDIC sweep, by account type.
• FDLXX vs. SPAXX: which Fidelity money fund keeps more after state tax.
• SPAXX vs. HYSA: whether stored cash should leave Fidelity for a bank.
• SPAXX vs. SGOV: spending cash in the core, stored cash in a Treasury bill ETF.
• SGOV vs. T-Bills: what buying bills yourself adds over a fund.
• Schwab Bank Sweep vs. SWVXX: the same question at Schwab, where cash defaults to a bank deposit.
• Emergency fund sizing: how much cash to hold before deciding where to hold it.

Sources

1. Fidelity, “Fidelity Cash Management Account” overview and FAQ (features, fees, ATM reimbursement, SPAXX 7-day yield as of October 6, 2026, the September 28, 2026 investment change, $4 million sweep coverage), read October 7, 2026. fidelity.com
2. Fidelity, “Cash Management Account FAQs” (core position options). fidelity.com
3. Fidelity, Cash Management Account Customer Agreement (order in which debits are paid; availability of electronic deposits). fidelity.com (PDF)
4. Fidelity, “Cash Available to Withdraw” balance definition. fidelity.com
5. FDIC, “National Rates and Rate Caps,” as of September 21, 2026 (interest checking 0.07%, $2,500 tier). fdic.gov
6. Fidelity, Cash Management Account core rates (FDIC-Insured Deposit Sweep 1.94% rate, 1.96% APY, effective October 6, 2026). fidelity.com
7. Fidelity, Fidelity Government Money Market Fund (SPAXX) summary, performance and composition pages (7-day yield, expense ratio, strategy, holdings and liquid assets as of September 30, 2026; returns against the FTSE 3-Month Treasury Bill index). fundresearch.fidelity.com
8. Fidelity, Fidelity Treasury Only Money Market Fund (FDLXX) summary (7-day yield as of October 6, 2026). fundresearch.fidelity.com
9. U.S. Department of the Treasury, Daily Treasury Bill Rates, October 6, 2026 (13-week coupon equivalent 4.14%). treasury.gov
10. Federal Open Market Committee, statement of September 16, 2026. federalreserve.gov
11. Federal Reserve Board, “Changes in U.S. Family Finances from 2019 to 2022: Evidence from the Survey of Consumer Finances,” October 2023, p. 16. federalreserve.gov (PDF)
12. Chris Wheat and George Eckerd, “Household Cash Buffer Management from the Great Recession through COVID-19,” JPMorgan Chase Institute, July 2023. jpmorganchase.com
13. Federal Reserve History, “Regulation Q.” federalreservehistory.org
14. Federal Reserve History, “Money Market Mutual Funds” (first fund in the early 1970s; the 1994 Community Bankers U.S. Government Fund episode). federalreservehistory.org
15. SRI International, “75 years of innovation: Cash Management Account (CMA).” sri.com
16. William J. Baumol, “The Transactions Demand for Cash: An Inventory Theoretic Approach,” Quarterly Journal of Economics 66(4), 1952, pp. 545–556. doi.org
17. James Tobin, “The Interest-Elasticity of Transactions Demand for Cash,” Review of Economics and Statistics 38(3), 1956, pp. 241–247. doi.org
18. Merton H. Miller and Daniel Orr, “A Model of the Demand for Money by Firms,” Quarterly Journal of Economics 80(3), 1966, pp. 413–435. doi.org
19. Itamar Drechsler, Alexi Savov and Philipp Schnabl, “The Deposits Channel of Monetary Policy,” Quarterly Journal of Economics 132(4), 2017, pp. 1819–1876. doi.org
20. Gara Afonso, Marco Cipriani, Catherine Huang, Abduelwahab Hussein and Gabriele La Spada, “Monetary Policy Transmission and the Size of the Money Market Fund Industry: An Update,” Liberty Street Economics, Federal Reserve Bank of New York, April 3, 2023. newyorkfed.org
21. Mark Egan, Ali Hortaçsu, Nathan Kaplan, Adi Sunderam and Vincent Yao, “Dynamic Competition for Sleepy Deposits,” NBER Working Paper 34267; summarized in the NBER Digest, January 2026. nber.org
22. FDIC, “Deposit Insurance at a Glance” ($250,000 per depositor, per insured bank, per ownership category; mutual funds not insured). fdic.gov
23. SIPC, “What SIPC Protects.” sipc.org
24. Fidelity, Cash Management Account FDIC-Insured Deposit Sweep program bank list. fidelity.com
25. SEC, press release 2009-104, “SEC Charges Operators of Reserve Primary Fund With Fraud,” May 5, 2009. sec.gov
26. Viktoria Baklanova, Isaac Kuznits and Trevor Tatum, “Prime Money Market Funds at the Onset of the Pandemic,” SEC Division of Economic and Risk Analysis staff note, 2021. sec.gov (PDF)
27. SEC, “Money Market Fund Reforms,” Release Nos. 33-11211; IC-34959, July 12, 2023, and fact sheet. sec.gov (PDF)
28. IRS, Topic No. 403, “Interest Received.” irs.gov
29. Fidelity, “2025 Percentage of Income from U.S. Government Securities,” supplemental letter (SPAXX 50.90%, marked as not meeting the California, Connecticut and New York minimum; FDLXX 98.67%). fidelity.com (PDF)

Author disclosure

Educational content, not investment or tax advice. Rates and returns are dated snapshots from the sources above; the state-tax percentages are 2025 figures that reset each year. Summitward has no affiliation with Fidelity.