Rebalancing your 401k almost never costs money at the moment you do it. The trades themselves are commission-free inside a standard plan, and no tax is owed when you sell one fund and buy another because the account is tax-deferred. The costs that do exist are indirect: the expense ratios of whatever funds you move into, advisory fees if you use a managed-account service, occasional redemption fees on funds sold too quickly, and a few situation-specific traps that can be far more expensive than any trading charge.
Why the Trades Themselves Are Free
Most 401k plans hold mutual funds or collective investment trusts rather than individual stocks. These funds are bought and sold at end-of-day net asset value, not on an open exchange, so there are no bid-ask spreads and no broker commissions to pay. Your plan’s recordkeeper processes exchanges in bulk through institutional share classes and absorbs the administrative cost as part of its service agreement with your employer. When you log in and shift money from a bond fund to a stock fund, nothing is deducted from the transaction.
No Taxes When You Sell Inside the Plan
This is the biggest financial advantage of rebalancing inside a 401k. Federal tax law treats the account as a tax-deferred trust, so selling a fund at a gain and reinvesting the proceeds generates no current tax liability. Tax is owed only when you eventually withdraw money, and distributions at that point are taxed as ordinary income.1Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
In a regular brokerage account, selling a fund with a $10,000 gain could trigger long-term capital gains tax of 0%, 15%, or 20%, or ordinary income rates if you held it under a year. Inside the 401k, that same sale keeps the full $10,000 invested and compounding. Over decades, that shielding is worth more than any of the small indirect costs discussed below.
Where the Real Costs Hide: Expense Ratios
The trade is free. The destination is not. Every mutual fund charges an expense ratio, an annual fee expressed as a percentage of your invested balance and deducted daily from the fund’s returns. Rebalancing from a low-cost index fund charging 0.03% into an actively managed fund charging 0.80% raises your ongoing cost on that portion of the portfolio by a factor of about 25.
On a $100,000 balance, the difference between 0.03% and 0.80% is roughly $770 a year, and it compounds. The fee never appears as a line item on your statement because it’s baked into the fund’s share price, which is exactly what makes it easy to miss. Before you move money into a new fund, pull up your plan’s fee disclosure and compare expense ratios. Every available option is listed there.
Managed Accounts and Advisory Fees
Many plans now offer managed account services or robo-advisors that handle rebalancing automatically based on your age, risk tolerance, and target retirement date. Advisory fees for these services typically run between 0.25% and 0.60% of your account balance per year, deducted quarterly, and they apply to the full managed balance regardless of whether any rebalancing happened that quarter. On a $200,000 balance, a 0.40% fee is $800 a year.
Federal law requires your plan to disclose all of these charges. The annual participant fee disclosure notice must itemize general plan administrative fees, investment-related expenses, and individual service charges such as advisory or brokerage fees.2eCFR. 29 CFR 2550.404a-5 – Fiduciary Requirements for Disclosure in Participant-Directed Individual Account Plans The disclosure is usually attached to a quarterly statement or posted on the plan’s online portal.
Redemption Fees and Short-Term Trading Restrictions
Some mutual funds charge a redemption fee when you sell shares too quickly after buying them. SEC rules cap this fee at 2% of the amount redeemed and only allow it on shares held for at least seven days.3eCFR. 17 CFR 270.22c-2 – Redemption Fees for Redeemable Securities Funds that impose one usually set it at 1% to 2% and define short-term as 30 to 90 days. The fee comes out of your sale proceeds and stays with the fund to compensate long-term shareholders for the costs created by rapid trading.
Plan providers also police round-trip trading: selling a fund and buying it back within a restricted window. Three round-trips in the same fund within 90 rolling days, or ten within 365, can trigger a suspension that blocks purchases in that fund for a set period. Rebalancing quarterly or less often almost never runs into this. Frequent tactical moves in the same fund can.
Self-Directed Brokerage Windows Are the Exception
About half of 401k plans now offer a self-directed brokerage window that lets participants invest in individual stocks, ETFs, and outside funds. If you use one, not every transaction is free. Fidelity’s BrokerageLink, for example, charges $0 for online stock and ETF trades but $32.95 for representative-assisted trades and $12.95 for automated phone orders, with per-contract fees on options.4Fidelity. Fidelity Brokerage and Commission Fee Schedule Check the schedule before placing orders through anything other than the online platform.
The Costly Trap With Employer Stock
If your 401k holds shares of your employer’s stock, selling them as part of a rebalance can quietly cost you far more than any fee. Net unrealized appreciation (NUA) is a tax provision that lets you pay long-term capital gains rates, capped at 20%, on the growth of employer stock when you eventually take a lump-sum distribution, rather than ordinary income rates that can reach 37%.5Office of the Law Revision Counsel. 26 USC 402 – Taxability of Beneficiary of Employees Trust
Sell the shares inside the plan and that benefit disappears. The proceeds become indistinguishable from any other plan asset and are taxed entirely as ordinary income at withdrawal. Federal law requires plans to allow diversification out of employer stock at least quarterly after three years of service on employer contributions, so the option to sell is always available.6eCFR. 26 CFR 1.401(a)(35)-1 – Diversification Requirements for Certain Defined Contribution Plans The point is to know what you’re giving up first. This matters most for people within a few years of retirement holding highly appreciated company shares.
Wash Sales When You Also Have a Taxable Account
Coordinating trades between a 401k and a taxable brokerage account can create a separate tax problem. The wash sale rule disallows a tax-deductible loss if you sell a security at a loss and buy a substantially identical one within 30 days on either side of the sale.7Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities
The IRS ruled in Revenue Ruling 2008-5 that buying substantially identical stock in an IRA within that 30-day window still triggers the rule, and the same logic applies to 401k purchases.8IRS. Revenue Ruling 2008-5 – Loss From Wash Sales of Stock or Securities When the replacement shares land in a retirement account, your cost basis doesn’t step up the way it would in a taxable wash sale. The disallowed loss is gone permanently, not deferred. Sell a fund at a loss in your brokerage account on Monday and let your 401k contribution buy the same fund on Friday, and the deduction is lost for good.
The Cheapest Way to Rebalance: Redirect Contributions
The lowest-cost rebalance is one that sells nothing. Change the allocation of your future payroll contributions to send more into the underweight funds. Over several pay periods, fresh money gradually pulls the portfolio back toward target with no redemption fees, no round-trip risk, and no wash sale exposure.
This works well when the drift is modest, around 5 percentage points or less. For larger imbalances, contribution rebalancing alone is too slow, and selling the overweight position is the practical fix. Most plan websites let you change contribution allocations in minutes, and the change takes effect within one or two pay cycles.
Target-Date Funds Do It for You
If you’d rather not handle any of this, a target-date fund holds a diversified mix of stocks and bonds and shifts more conservative as you approach retirement. The manager does the internal rebalancing, and there’s no separate charge for it. The cost is built into the fund’s expense ratio, which for index-based target-date funds can run as low as 0.10% to 0.15%.
What Doing Nothing Costs
The hidden expense in this discussion is skipping rebalancing altogether. A portfolio left alone gradually tilts toward whichever asset class has performed best. After a long bull market, a 60/40 stock-bond mix can drift to 80/20, carrying far more volatility than you signed up for. The point of rebalancing isn’t to squeeze out extra return. It’s to keep your risk where you intended so you don’t panic-sell during a downturn. Given that the trades are free and tax-free inside the plan, the indirect costs are almost always small compared to the cost of drifting out of your intended allocation.