How Often Should You Invest? Daily, Weekly, or Monthly

The $5-a-Day Portfolio

I get paid once a month. A day or two after that paycheck lands, I log in and buy, and the only judgment call I make is which fund gets the money. There is no recurring transfer, no daily drip, no fractional share autopilot. Every large brokerage will now invest $5 for me every trading day, and people reasonably ask why I don’t let them.

Fractional shares fixed a real problem. FINRA’s investor guide lists the benefits plainly: access to higher-priced stocks and ETFs, diversification for small accounts, more precise portfolio balancing, and full use of funds, since “investors who only buy whole shares might end up having some cash left over.”¹⁹ A person with $25 a week can now own a diversified portfolio down to the penny. That is a genuine improvement over odd-lot minimums and $7 commissions.

The step that needs scrutiny comes later, when the ability to invest any dollar amount gets treated as evidence that five purchases of $5 beat one purchase of $25.

What a Cadence Can Change

Frequency cannot change your savings rate, your asset allocation, your expense ratios, or the returns the market delivers. It changes the average number of days your money spends in cash on its way into the market, and it changes how many separate purchase records you accumulate. That is the whole list.

Our lump sum versus dollar-cost averaging guide works through the adjacent question: what to do when a large sum is already sitting in your account. This guide is about the recurring decision, where the money arrives on a schedule you don’t control.

Daily Buying Spreads a Paycheck That Already Landed

The intuitive case for daily investing is that each dollar goes to work sooner. Follow the cash and that reverses. You cannot invest income before you are paid. A daily recurring purchase takes a paycheck that has already hit your account and feeds it into the market over the following weeks, which means the average dollar reaches the market later than it would if you invested the whole paycheck on the day it arrived.

That is cost averaging, and Vanguard has measured what it costs. Using the MSCI World Index from 1976 to 2022, an immediate lump-sum investment beat splitting the same money into three monthly installments 68% of the time over a one-year horizon, with the caveat that the study assumed “no interest earned on any uninvested portion.” Crediting the waiting cash with three-month Treasury bill interest, the figure falls to 65%, and Vanguard notes that “as cash interest increases, LS’s advantage diminishes.”¹ An earlier Vanguard study using rolling 10-year periods found a 60/40 lump sum averaged 2.3% more than a 12-month schedule in the US market.²

Both papers are explicit that this does not describe paycheck investing. The 2012 paper’s sidebar says that when investable cash arrives in small amounts over time, periodic investing is “a prudent way to invest (and really the only sound alternative to accumulating that money in cash and then actively trying to time the market at some later point),” and that its research instead “focuses on the strategies for investing an immediately available large sum of money.”² So the two-thirds figure has nothing to say about whether I should buy weekly or monthly. It has plenty to say about the RSU proceeds that land in my account four times a year, which are a lump sum by any definition.

What the Waiting Costs

Here is the arithmetic for my own situation: monthly pay, five cadence options, measured against the benchmark of investing each paycheck on the day it arrives.

No cadence in that table gets money in sooner than monthly, because none of them can invest a paycheck before it arrives. They differ only in how slowly the paycheck goes in afterward, and the finer the slices, the longer the average dollar waits. Daily buying is the slowest of the sub-monthly options and creates 21 times as many tax lots. Quarterly batching is the one direction that genuinely delays money, and it costs about twice as much as the daily drip.

The dollar figures use a premium of 3.65%, which is a 7% assumed portfolio return against the 3.35% seven-day yield on Fidelity’s government money market fund as of September 19, 2026.²⁵ The premium is the number that matters, and it is far smaller than a gross return assumption suggests. Vanguard’s federal money market fund was near 3.58%, the best high-yield savings accounts reached 4.50%, and the national average savings rate sat between 0.38% and 0.45%.²⁵ Those three choices change the answer more than cadence does:

Now put those figures next to the randomness they are competing with. At 16% annualized volatility, the standard deviation of a 14.5-day equity exposure is about 3.19%, or roughly $3,186 on $100,000. The market noise over the window is about 22 times the expected value being optimized. Any single year’s outcome is decided by which weeks you happened to buy in rather than by the cadence rule that produced them. Every figure here is an expected value under stated assumptions.

Where the Behavioral Evidence Is Strong

The case for automatic investing does not rest on returns, and it is well supported. Madrian and Shea studied one large employer that switched to automatic 401(k) enrollment and found participation of 37% among employees hired under opt-in, against 86% for employees with similar tenure hired under automatic enrollment.³ Thaler and Benartzi’s Save More Tomorrow program asked employees to commit future raises to saving in advance; 78% joined, 80% stayed through four raises, and average contribution rates went from 3.5% to 13.6% over 40 months.⁴

Both findings deserve their caveats. Madrian and Shea’s defaults cut in two directions at once: 76% of automatically enrolled participants stayed at the default 3% contribution rate, and 80% of their contributions went into a money market fund, an allocation almost nobody would choose deliberately.³ The Save More Tomorrow result comes from 162 employees at one anonymous manufacturer, was not randomized, and the comparison group that accepted a financial consultant’s advice went from 4.4% to 8.8% over the same period, so the honest gap is 13.6% against 8.8%.⁴ What both studies measure is the power of defaults and commitment. The magnitude dwarfs anything cadence can do: a contribution rate that goes from 3.5% to 13.6% is worth thousands of times more than two weeks of earlier market exposure.

What the Evidence Says About Daily

Automation and frequency are separate claims, and only the first one has support. I could not find a single study testing daily against weekly against monthly contributions on either returns or savings persistence for retail investors. Two adjacent findings are worth more than the absent one.

The closest direct test comes from a randomized field experiment in Sri Lanka that unbundled deposit frequency from the other features of savings collection. De Mel, McIntosh and Woodruff found that “frequency and salience affect the number of transactions, but not the level of savings.”⁵ The number of deposits went up and the amount saved did not. The setting is rural bank deposits rather than a US brokerage app, so treat it as suggestive.

The second finding explains why daily investing feels so effective. Hershfield, Shu and Benartzi ran a field experiment on how a savings program was described and found that framing a deposit as $5 per day instead of $150 per month quadrupled enrollment, and erased an income gradient: under monthly framing, three times as many top-bracket as bottom-bracket consumers signed up, and under daily framing that gap disappeared.⁶ The experiment varied only the description of the program, leaving the deposit schedule alone, and the outcome it measured was sign-up rather than how much people eventually saved. Daily language recruits savers, which makes $5-a-day a useful way to set a budget target while the purchases themselves stay monthly.

Theory points the same way. Kirkby, Mitra and Nguyen modeled splitting a fixed sum into more installments and proved that expected terminal wealth “is monotonically decreasing” in the number of installments, while variance behaves non-monotonically and “tends to increase for large” numbers of splits.⁷ Their model splits an existing lump sum and contains no wage income, so it speaks to how finely you slice available cash rather than to paycheck cadence.

There is also a cost to building a daily relationship with a brokerage app. Kalda, Loos, Previtero and Hackethal used transaction-level data from two German banks and found that after investors began using smartphone apps, purchases of riskier, lottery-type and past-winner assets rose by roughly 67%, and that assets bought on smartphones delivered lower returns.⁸ Earlier experimental work by Thaler, Tversky, Kahneman and Schwartz found that subjects shown results less often chose more risk, which paid off within the returns their experiment used.⁹ Neither study indicts recurring contributions, which are the opposite of discretionary trading. Both make me skeptical of any plan whose selling point is that I will open the app more often.

Brokerages are careful about what they claim. Fidelity says recurring investments help you “build a lasting routine” and then discloses that “dollar cost averaging does not assure a profit or protect against a loss in declining markets.”¹⁰ Robinhood says recurring investing can “help make investing a habit and build your portfolio long term.”¹¹ Both statements are about habit formation, neither cites research, and neither claims a return advantage.

Tax Lots Multiply Fast

A tax lot is one acquisition of a security with its own date and cost basis. IRS Publication 550 sets the default: if you cannot adequately identify the shares you sold, “the basis of the securities you sell is the basis of the securities you acquired first,” which is first in, first out.¹³ Specific identification is what lets you choose instead, and our guide to SpecID and tax lots covers the mechanics.

Three funds bought monthly for a decade produce about 360 lots. The same three funds bought every trading day produce about 7,560, before dividend reinvestment adds more.

Two corrections to the scary version of this story. First, the paperwork is mostly handled: brokers must report adjusted basis and acquisition date for covered securities, which includes stock acquired for cash after 2010 and regulated investment company shares after 2011, and the Form 8949 instructions let you skip itemizing entirely and enter aggregate totals on Schedule D when basis was reported to the IRS and no adjustment appears in box 1f or 1g.¹⁵¹⁶ Thousands of lots do not mean thousands of form lines. The exception does stop applying to any lot carrying a wash-sale adjustment in box 1g, which is exactly the lot a frequent buyer who harvests losses will create.

Second, choosing lots is easier than folklore suggests. The regulations allow identification up to the earlier of settlement or the required settlement time, and a standing order or instruction, such as a broker’s highest-cost or tax-efficient default, “is treated as an adequate identification made at the time of sale.”¹⁴ Average cost is also available for mutual fund and most ETF shares, since Publication 550 extends it to shares in “a mutual fund (or other regulated investment company),” though not to ordinary individual stocks held outside a dividend reinvestment plan.¹³

What survives is narrower and still real. Lot-level choice has economic value in a taxable account, and every lot you add is one more row your broker’s software has to get right, one more holding-period boundary, and one more input into a loss-harvesting decision.

The Case That More Lots Help

The strongest argument against everything above is that granular lots at varied cost bases give you more harvestable losses. Wealthfront makes it directly: tax-loss harvesting “can add more value to clients who make regular deposits into their accounts compared to ones who make a single deposit,” because “if you add more deposits, you have more recently purchased holdings” sitting near current prices.²² This is the mechanism direct indexing relies on.

The same whitepaper marks where the argument stops, and it stops at daily: “very frequent deposits (for example, less than 30 days apart) may actually decrease our software’s ability to harvest losses in the short term. This is because more frequent deposits can result in multiple tax lots in the same stock, which can prevent tax-loss harvesting due to our attempt to avoid wash sales.”²² Regular deposits help harvesting up to roughly monthly, and sub-30-day deposits work against it.

The direct-indexing comparison also does not transfer cleanly. Its edge comes from holding hundreds of different stocks whose returns disperse, so some are down while the index is up. Buying one ETF on 250 different days gives you 250 lots whose prices move together, which produces far less independent harvestable loss. These are vendor materials describing harvesting yield rather than after-tax return, so weigh them accordingly.

Recurring Buys and the Wash-Sale Window

A wash sale happens when you sell at a loss and within 30 days before or after the sale you buy substantially identical securities, acquire them in a taxable trade, acquire an option on them, or buy them inside your IRA or Roth IRA.¹³ A recurring purchase schedule means a buy order is always inside that 61-day window. Our tax-loss harvesting guide covers the replacement-fund mechanics.

The matching rule decides how much of a loss survives, and it works share for share in purchase order. Publication 550’s example sells 100 shares at a $1,000 loss with 75 replacement shares bought in the window: $750 of the loss is disallowed on the 75 matched shares and $250 remains deductible on the other 25.¹³ A daily purchase of a few shares therefore defers only the matched fraction. Once your replacement purchases equal or exceed the shares you sold, the entire loss is disallowed.

Your broker’s reporting does not cover the whole rule. The Form 1099-B instructions require a broker to report a disallowed loss only “if both the sale and purchase transactions occur in the same account with respect to covered securities with the same CUSIP number.”¹⁵ Your own obligation covers substantially identical securities in any account at any broker, including purchases by your spouse. Whether two different S&P 500 ETFs are substantially identical is unsettled, and no 1099-B will ever raise the question for you.

A replacement purchase inside an IRA costs more than one in a taxable account, because the deferral mechanism does not apply. Revenue Ruling 2008-5 holds that when an individual sells at a loss and causes their IRA or Roth IRA to buy substantially identical securities inside the window, “the loss on the Sale of stock is disallowed under § 1091, and A’s basis in the individual retirement account or Roth IRA is not increased by virtue of § 1091(d).”¹⁷ There is no basis adjustment to recover the deduction later, so the loss is gone. An automatic weekly purchase of a total-market fund inside a Roth IRA, combined with harvesting the same exposure in taxable, is a standing trap.

Fractional Shares and the Exit Door

Dollar-based recurring orders produce fractional shares, and fractions behave differently from whole shares in ways worth knowing before you accumulate a decade of them.

The SEC’s investor bulletin states that “you generally cannot transfer fractional shares to another brokerage firm. If you decide to transfer your brokerage account to a different brokerage firm you may have to sell any fractional shares in your account.”¹⁸ FINRA is blunter: you have to sell them first, “potentially incurring taxes and fees.”¹⁹ Fidelity, Schwab and Interactive Brokers all say the same about transfers out, and Robinhood states that its fractional shares “are illiquid outside of Robinhood and aren’t transferable.”¹² In a taxable account, changing brokers becomes a taxable sale of every fraction you own.

Execution differs too. The SEC bulletin notes that some firms aggregate fractional orders through the day rather than filling them in real time, and that “the process your brokerage firm uses to handle buying and selling of fractional shares may impact the price you pay or receive,” while some firms allow only market orders.¹⁸ Robinhood’s recurring orders specifically are grouped into batch market orders processed between 11 AM Eastern and the close, filled at a weighted average price, while its ordinary fractional orders execute in real time.¹¹

Spread costs do not multiply with order count. Half the spread scales with the dollars traded, so 250 purchases of $48 in a liquid ETF cost about what one $12,000 purchase costs, and there are no commissions to stack. The size-dependent effects are smaller and harder to see: odd lots are generally ineligible for inclusion in the national best bid and offer,²⁰ and when the SEC amended its execution-quality rules it agreed with commenters that “full share price improvement statistics are not informative for the execution quality of fractional trades,” adding separate reporting categories whose compliance date is August 1, 2026.²¹ Comparable data is only now arriving. The measurable effect is a few basis points of execution drag plus less control over order type and fill timing.

New Money as a Rebalancing Trade

This is the part of my process that automation would cost me. Vanguard tells investors to “move dividends and interest to your portfolio’s underweighted asset classes” instead of buying and selling to rebalance.²³ Fidelity extends it to contributions: “if you’re planning to contribute more to your investments soon, another option is to use those new contributions to rebalance,” and notes that rebalancing inside a brokerage account “can trigger tax consequences if you are selling part of a position.”²⁴ Our rebalancing guide covers the Vanguard evidence that cash flows alone controlled risk from 1926 to 2009 with zero portfolio turnover.

A recurring purchase that buys target weights every day keeps buying whatever is already overweight. My monthly purchase can go entirely to the sleeve that has fallen behind. Nobody publishes a figure for what that is worth, and I would not trust one, because the benefit is simply the capital gains tax you never realized. If fixing drift by selling would have realized $10,000 of long-term gain at a 23.8% federal rate, directing new money instead is worth $2,380 in deferred tax, and that number is arithmetic on your own situation rather than a research result.

Two kinds of discretion look similar from the outside. Deciding when to invest based on how the market feels is timing. Deciding which underweight sleeve receives a fixed monthly purchase is portfolio maintenance. I keep the first fixed and allow myself only the second.

When Daily Investing Is the Right Call

My cadence suits my situation, and several situations point the other way.

• You don’t reliably invest otherwise. If cash sits for months while you wait for a good moment, a daily or weekly automatic purchase beats your actual behavior by far more than two weeks of timing could ever cost. The Madrian and Shea and Save More Tomorrow results are about exactly this gap.
• It is a tax-advantaged account. Inside a 401(k), IRA, Roth or HSA there are no lots to select, no wash sales to trip, and no gains to realize when you rebalance. Buy daily if you enjoy it.
• Your income is irregular. Variable commissions, freelance invoices or tips arrive continuously, so there is no payday to invest on, and a frequent sweep genuinely shortens the time cash sits idle.
• Your cash earns nothing. If contributions wait in a checking account at 0.40% instead of a money market fund, the premium you are giving up roughly doubles, and shortening the wait matters more.
• The daily framing is what gets you to save. Budgeting in $5-a-day terms is well supported by the enrollment research. You can keep the framing and still execute monthly.

My Rule

I invest on a fixed date each month, a day or two after I am paid, and I send the money to whichever sleeve is furthest below target. RSU proceeds go in at vest, in full, because a vest is a lump sum and the Vanguard evidence applies to it directly. I do not spread a vest across the following quarter, and I do not wait for a better entry.

Manual investing earns its keep only while the rule stays calendar driven: on the 3rd, I invest what is available. A rule that becomes “sometime this month, if stocks seem reasonably priced” has turned into market timing with extra steps. If I ever skip a month, the right response is to automate the purchase and accept target-weight buying, because a savings rate that drifts 3 percentage points too low costs far more than lot proliferation ever will.

Try It: The Investing Cadence Calculator

Set your pay schedule, your cadence and your assumptions. The bar chart shows the expected cost of each cadence against investing on payday, and the dashed line shows one standard deviation of market movement over the same waiting window, which is the scale everything here is competing with.

Frequently Asked Questions

Is investing daily better than investing monthly?

Not in expected return. If you are paid monthly and invest on payday, a daily schedule spreads a paycheck you already received across the following weeks, so the average dollar reaches the market about 14 days later. At a 3.65% assumed premium over cash that is roughly $142 per $100,000 of annual contributions, against a standard deviation of market moves over the same window worth about $3,186. Daily investing wins only when the alternative is not investing.

Does buying more often lower my average cost per share?

It lowers your average cost relative to the average price paid over the period, which is a mathematical property of buying fixed dollar amounts and not a source of profit. The benchmark that matters is what else the money could have done. Vanguard found immediate investment beat a three-month schedule 68% of the time with no interest on the waiting cash, and 65% when the cash earned Treasury bill interest.

How many tax lots is too many?

There is no threshold in the tax code. Brokers must track basis for covered securities, and the Form 8949 instructions let you report aggregate totals on Schedule D when basis was reported and no box 1f or 1g adjustment applies, so lot count alone does not create filing work. The practical limits show up when you harvest losses, since a wash-sale adjustment forces that lot to be itemized, and when you want to choose specific lots to sell.

Does my broker handle wash sales for me?

Only partly. A broker must report a disallowed loss when the sale and purchase happen in the same account in securities with the same CUSIP. Your own obligation extends to substantially identical securities in every account you and your spouse hold, at any firm. Purchases inside an IRA are the worst case: under Revenue Ruling 2008-5 the loss is disallowed and the IRA gets no basis increase, so the deduction is gone permanently.

Should I automate my contributions or invest manually?

Automate if there is any chance you will skip. Manual investing earns its keep only when it is calendar-driven and buys the underweight part of the portfolio, which both Vanguard and Fidelity recommend as a way to rebalance without selling. A missed month costs more than the tax advantages of manual investing recover.

Does any of this matter inside a 401(k)?

Very little. Payroll deferrals already invest on payday, and there is no lot-level tax management to preserve, no wash-sale exposure and no realized gains on rebalancing. Cadence questions are a taxable-account concern.

What about crypto?

The wash-sale rule applies to stock and securities, and digital assets are treated as property, so it does not currently reach crypto. Legislation to extend it has been introduced and referred to committee, not enacted. Broker reporting on digital assets is phasing in through Form 1099-DA, with gross proceeds for 2025 transactions and basis for covered digital assets from 2026.

Related Guides

• Lump Sum vs. Dollar-Cost Averaging: 98 Years of Evidence for what to do with money that is already available.
• How Often Should You Rebalance Your Portfolio? for bands, triggers and rebalancing with cash flows.
• How to Sell Tax-Efficiently: SpecID and Tax Lots for choosing which lots to sell.
• Tax-Loss Harvesting for the wash-sale window and replacement funds.
• The RSU Bridge Strategy for how vest proceeds fit into monthly cash flow.
• Just Keep Buying: A Strong Habit, Not a Complete Plan for where the accumulation rule stops applying.

Key Takeaways

• Cadence controls how long a dollar waits in cash and how many tax lots you create. It cannot change your savings rate, allocation or returns.
• Daily purchases spread a paycheck that has already arrived, so for a monthly payee who invests on payday they delay the average dollar by about 14 days rather than accelerating it.
• For one modeled monthly payee at a 3.65% premium over cash, that delay is worth roughly $142 per $100,000 of annual contributions, against a one standard deviation market move of about $3,186 over the same window.
• Automatic saving has strong evidence behind it: 37% against 86% participation under automatic enrollment, and 3.5% to 13.6% contribution rates under Save More Tomorrow. Neither study tested frequency.
• The one randomized test that isolated deposit frequency found it changed the number of transactions and not the level of savings. Framing a deposit as $5 per day quadrupled enrollment, which is a finding about language rather than schedules.
• Three funds bought daily generate about 7,560 lots per decade against 360 bought monthly, and Wealthfront reports that deposits less than 30 days apart can reduce its ability to harvest losses.
• In a tax-advantaged account none of the lot-level costs exist, so daily investing there is close to free.
• Invest each inflow promptly and let its size pick the cadence: payroll on payday, a vest at vest, and discretion limited to which underweight sleeve receives the money.

Sources

1. Vanguard Research. “Cost averaging: Invest now or temporarily hold your cash?” Megan Finlay and Josef Zorn, February 2023. corporate.vanguard.com
2. Vanguard Research. “Dollar-cost averaging just means taking risk later.” Anatoly Shtekhman, Christos Tasopoulos and Brian Wimmer, July 2012. vanguard.com (PDF)
3. Brigitte C. Madrian and Dennis F. Shea. “The Power of Suggestion: Inertia in 401(k) Participation and Savings Behavior.” Quarterly Journal of Economics 116(4), 2001, 1149–1187. academic.oup.com
4. Richard H. Thaler and Shlomo Benartzi. “Save More Tomorrow: Using Behavioral Economics to Increase Employee Saving.” Journal of Political Economy 112(S1), 2004, S164–S187. journals.uchicago.edu
5. Suresh de Mel, Craig McIntosh and Christopher Woodruff. “Deposit Collecting: Unbundling the Role of Frequency, Salience, and Habit Formation in Generating Savings.” American Economic Review 103(3), 2013, 387–392. aeaweb.org
6. Hal E. Hershfield, Stephen Shu and Shlomo Benartzi. “Temporal Reframing and Participation in a Savings Program: A Field Experiment.” Marketing Science, 2020. pubsonline.informs.org
7. J. Lars Kirkby, Sovan Mitra and Duy Nguyen. “An analysis of dollar cost averaging and market timing investment strategies.” European Journal of Operational Research 286(3), 2020, 1168–1186. sciencedirect.com
8. Ankit Kalda, Benjamin Loos, Alessandro Previtero and Andreas Hackethal. “Smart(Phone) Investing? A within Investor-Time Analysis of New Technologies and Trading Behavior.” NBER Working Paper 28363, January 2021. nber.org
9. Richard Thaler, Amos Tversky, Daniel Kahneman and Alan Schwartz. “The Effect of Myopia and Loss Aversion on Risk Taking: An Experimental Test.” Quarterly Journal of Economics 112(2), 1997, 647–661. academic.oup.com
10. Fidelity. “Recurring investments.” Read September 2026. fidelity.com
11. Robinhood. “About recurring investments and orders.” Read September 2026. robinhood.com
12. Robinhood. “Fractional shares.” Read September 2026. robinhood.com
13. Internal Revenue Service. Publication 550, “Investment Income and Expenses” (2025). Identifying stock or bonds sold; Average Basis; Wash Sales. irs.gov (PDF)
14. 26 CFR § 1.1012-1(c), including (c)(8) on standing orders and instructions. law.cornell.edu
15. Internal Revenue Service. “Instructions for Form 1099-B,” revised April 30, 2026. Covered securities; Wash sales. irs.gov
16. Internal Revenue Service. “Instructions for Form 8949” (2025), Exception 1, and Instructions for Schedule D (Form 1040). irs.gov
17. Internal Revenue Service. Revenue Ruling 2008-5, I.R.B. 2008-3. irs.gov (PDF)
18. U.S. Securities and Exchange Commission, Office of Investor Education and Advocacy. “Fractional Share Investing: Buying a Slice Instead of the Whole Share.” November 9, 2020. investor.gov
19. FINRA. “Investing in Fractional Shares.” June 26, 2025. finra.org
20. Office of Financial Research. “There When You (Don’t) Need It: The Reliability of Odd-Lot Liquidity.” Working Paper 25-01, June 5, 2025. financialresearch.gov (PDF)
21. U.S. Securities and Exchange Commission. “Disclosure of Order Execution Information,” Release 34-99679, adopted March 6, 2024. sec.gov (PDF)
22. Wealthfront. “Tax-Loss Harvesting” whitepaper. Read September 2026. Firm-published material describing its own service. research.wealthfront.com
23. Vanguard. “Rebalancing your portfolio.” Read September 2026. investor.vanguard.com
24. Fidelity. “Rebalancing your investments.” Read September 2026. fidelity.com
25. Cash yields as of mid-September 2026: Fidelity Government Money Market Fund (SPAXX) seven-day yield fidelity.com; Vanguard Federal Money Market Fund (VMFXX) vanguard.com; savings and money market account averages bankrate.com

Editor’s note

Written September 2026. Tax rules described are US federal rules for taxable brokerage accounts and retirement accounts; state treatment and your own situation may differ. Cash yields move, and the cadence figures here scale directly with the premium between your portfolio’s expected return and the yield on cash, so rerun the calculator with your own assumptions rather than relying on the illustrative dollar amounts. Expected values are not forecasts.