Rebalancing Your Long-Term Portfolio
Left alone, a 60/40 portfolio slowly becomes 75/25 as stocks run — quietly raising your risk. Rebalancing pulls it back, and it forces you to buy low and sell high.
Don't have time? Here's what you need to know:
- 1Markets cause drift: a 60/40 portfolio can become 75/25 after a stock run, quietly raising your risk.
- 2Calendar (annual), threshold (~5-point band), or a hybrid of both are all valid rebalancing methods.
- 3Rebalancing mechanically sells what's run up and buys what's down — but its main job is risk control, not returns.
- 4Rebalance with new contributions first, and do taxable sales inside IRAs or 401(k)s to minimize the tax bill.
Why Your Portfolio Drifts Away From Its Target
Suppose you set a 60% stock, 40% bond portfolio. Stocks tend to outgrow bonds over time, so after a strong few years that mix might drift to 70/30 or 75/25 without you doing anything. The portfolio you actually hold is now riskier than the one you chose — and you would feel that the hard way in the next downturn.
Drift cuts both ways. After a stock crash, your equity slice shrinks and you end up more conservative than intended, right when stocks are cheapest. Rebalancing is the act of resetting the weights back to target, and its value is precisely that it forces you to act against the recent trend rather than with it.
Calendar vs Threshold Rebalancing
There are two main approaches, and both work. Calendar rebalancing means checking on a fixed schedule — typically once a year — and resetting to target regardless of how far things have moved. It is simple and easy to automate. Threshold rebalancing means acting only when an allocation drifts beyond a set band, commonly about five percentage points from target, ignoring smaller wiggles.
Many investors combine the two: check on a calendar (say, annually) but only trade if the drift exceeds the threshold. This keeps you disciplined without overtrading on noise. Rebalancing too often adds transaction costs and, in taxable accounts, taxes — while rebalancing too rarely lets risk creep up. Once a year, or at a ~5-point band, is a sensible middle for most long-term portfolios.
| Method | Trigger | Pros | Watch out for |
|---|---|---|---|
| Calendar | Fixed date (e.g. annual) | Simple, easy to automate | May trade when drift is tiny |
| Threshold | Drift past a band (e.g. 5%) | Acts only when it matters | Requires periodic monitoring |
| Hybrid | Check on date, act past band | Disciplined, low overtrading | Slightly more to track |
Tip: An annual check combined with a ~5-percentage-point threshold captures most of rebalancing's benefit while minimizing trades, taxes, and effort.
How Rebalancing Forces Buy-Low, Sell-High
Rebalancing is a mechanical, emotion-free way to do what investors find nearly impossible by feel. To return to target after stocks have surged, you sell some stocks (the thing that ran up) and buy bonds — trimming high. After a crash, you sell some bonds and buy stocks while equities are down — buying low. You are systematically selling what is expensive and buying what is cheap, without having to predict anything.
Its primary purpose, though, is risk control, not return enhancement. Rebalancing keeps your portfolio's risk level near what you intended; the buy-low, sell-high behavior is a welcome side effect that may modestly help returns in choppy markets. Do not expect rebalancing to dramatically boost performance — expect it to keep you from quietly drifting into a portfolio far riskier than you meant to hold.
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Rebalancing Without a Big Tax Bill
In a taxable account, selling appreciated holdings to rebalance can trigger capital-gains tax, which eats into the benefit. The cleanest fixes avoid selling altogether. Direct new contributions and reinvested dividends toward whichever asset is underweight — over time this nudges you back to target with no taxable sales at all. For retirees, drawing withdrawals from the overweight asset accomplishes the same thing.
When you do need to trade, prefer rebalancing inside tax-advantaged accounts like an IRA or 401(k), where sales create no tax bill. Reserve actual selling in taxable accounts for when drift is large enough to matter and contributions alone cannot fix it. Combined with an annual or threshold check, these habits keep your asset allocation on track at minimal cost.
Important: Rebalancing by selling in a taxable account can trigger capital-gains tax. Rebalance with new contributions first, and do tax-generating trades inside IRAs or 401(k)s where possible.
Frequently Asked Questions
How often should I rebalance my portfolio?
For most long-term investors, once a year is plenty, or whenever an allocation drifts more than about five percentage points from its target. Rebalancing more often adds costs and taxes without much benefit; rebalancing too rarely lets risk creep up. An annual check combined with a threshold band is a sensible default.
What's the difference between calendar and threshold rebalancing?
Calendar rebalancing resets your portfolio on a fixed schedule, like annually, regardless of drift. Threshold rebalancing acts only when an allocation moves beyond a set band, often around five percentage points. Many investors combine them: check on a date but trade only if drift exceeds the threshold, which limits unnecessary trading.
Does rebalancing improve my returns?
Its main job is controlling risk, not boosting returns. By restoring target weights, rebalancing keeps your portfolio from drifting into a riskier mix than you intended. The buy-low, sell-high mechanism can modestly help returns in volatile, range-bound markets, but you should view rebalancing primarily as risk management.
How do I rebalance without paying a lot of tax?
Avoid selling where you can. Direct new contributions and dividends to whichever asset is underweight to drift back toward target without taxable sales. Do any necessary selling inside tax-advantaged accounts like an IRA or 401(k), where trades create no tax bill. Reserve taxable-account sales for large drifts that contributions alone can't fix.
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Alex Harrington
CFA Level II Candidate, Finance & Economics
Alex Harrington is an independent ETF researcher and personal finance writer with over 8 years of experience analyzing exchange-traded funds. A CFA Level II candidate with a background in economics, Alex has reviewed 800+ ETFs and helped thousands of beginners build their first investment portfolios through clear, jargon-free education.
This content is for educational purposes only and does not constitute financial advice. Past performance does not guarantee future results. Consult a licensed financial advisor before making investment decisions.