Do I need to rebalance my portfolio?
Last updated August 2026
Short answer
People look for evidence that rebalancing improves returns, do not find it, and conclude it is unnecessary. The evidence was never the argument.
What happens if you never do it
Winners grow into a larger share of the portfolio, so a 70/30 mix can drift toward 85/15 over a strong decade.
The change happens in the direction that increases risk, and it happens most in the periods where increasing risk feels most comfortable.
You discover the actual allocation during the next downturn, which is the worst moment to learn it.
Why the return argument is a distraction
Over long rising periods, trimming winners can reduce returns slightly relative to letting them run.
That is a genuine finding and it is not an argument against rebalancing, because return was never the objective.
The objective is holding the risk you chose, which is the thing that determines whether you stay invested at all.
Who can skip it
Anyone holding a single target-date or balanced fund, which rebalances internally as part of the product.
Anyone whose plan offers automatic rebalancing and has switched it on.
Holding a target-date fund alongside other funds does not qualify, because the overall allocation still drifts even though the fund itself does not.
Try it in Walnut
Walnut connects to your brokerage and shows what your allocation has actually become, which is the number this decision depends on.
Doing it without a tax bill
Direct new contributions into whatever is underweight, which uses money that was going in anyway.
Switch off automatic dividend reinvestment so distributions arrive as cash you can point at the laggard.
Do any selling inside retirement accounts first, where no taxable event occurs.
How much effort it deserves
For a small balance, contributions alone will usually keep the allocation close enough.
For a large one, an annual check with a drift threshold is proportionate and takes minutes.
Checking monthly is not more diligent, it is just more trading, and in a taxable account it is more tax.
The version that actually fails
Deciding case by case, in the moment, which turns every rebalance into an argument about markets.
Rebalancing after a rise and skipping it after a fall, which is the pattern most people follow by instinct.
Changing the target instead of rebalancing to it, which is how a plan quietly becomes whatever recently performed well.
What to check while you are there
Drift inside an asset class, not only between classes, since an equity allocation at exactly target can still be concentrated in a handful of names.
Overlap between funds, which increases exposure without changing any label on the account.
Whether the target still matches your horizon, because a mix chosen a decade ago was set for a different length of time than remains.
Sources
Guidance on asset allocation, diversification and rebalancing is published by the SEC at investor.gov, with capital gains treatment at IRS Topic no. 409. Walnut is informational and is not an investment adviser. This guide is educational and not personalized investment advice.
FAQ
Do I need to rebalance?
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If you chose a target allocation and want to keep it, yes, because markets move it continuously. If you hold a single target-date fund, no, because it rebalances internally and that is what you are paying it for.
Does it increase returns?
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Not reliably. Over long rising periods, trimming winners can slightly reduce return. The purpose is keeping risk where you set it, which is a different objective from maximising the outcome.
What happens if I never do it?
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The portfolio drifts toward whatever performed best, which raises risk exactly when it feels safest. A 70/30 mix can become 85/15 over a strong decade, and the first serious decline is when you find out.
How often is enough?
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Annually, or when an allocation drifts beyond a threshold such as five percentage points. More frequent adjustment mostly adds costs and, in a taxable account, tax.
Do I have to sell anything?
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Frequently not. Directing new contributions into whatever is underweight, and taking dividends as cash rather than reinvesting them, corrects drift without a single sale or taxable event.
What if it is all in a 401(k)?
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Then it is straightforward, because selling inside the plan creates no tax. Many plans also offer automatic rebalancing on a schedule, which removes the task entirely once switched on.
Should I rebalance after a crash?
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That is when it matters most and feels worst, because the rule says buy more of what just fell. Having the trigger set in advance is what makes the action possible at all.
Is it worth it for a small portfolio?
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The principle holds and the effort should scale. For a small balance, directing new contributions is usually sufficient, and a formal rebalance can wait until the amounts involved justify the attention.
What else should I check at the same time?
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Drift inside an asset class as well as between them, overlap between funds that quietly raises concentration, and whether the target itself still matches your horizon. A mix chosen a decade ago was set for a longer period than now remains.
Can my broker do it automatically?
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Many workplace plans offer scheduled automatic rebalancing, and switching it on removes the task entirely. Retail brokerage accounts less often do, which is why the contribution-based approach is the practical route for a taxable portfolio.