When to Rebalance Your Portfolio and When to Do Nothing
Rebalancing is not about timing the market. It is about controlling risk. Here is the framework that keeps you from overreacting.
Take Jordan, a 41-year-old who works in marketing and has done everything right. She picked a simple portfolio, meaning the full collection of investments a person owns across all their accounts, set at 70 percent stocks and 30 percent bonds, invested consistently for years, and ignored the noise. Then she checks her account one afternoon and discovers it is now 88 percent stocks.
She did not choose more risk. The market chose it for her, quietly and automatically, with no permission required. Most investors have strong opinions about what to buy and no system whatsoever for when to rebalance. That is the skill this article covers.
What Rebalancing Actually Is
Rebalancing is maintenance. It is the process of restoring a portfolio to its original target percentages after market movements have caused those percentages to drift away from what was intended. Think of it like a car that slowly pulls to the right over time. Nothing dramatic happened. It just needs to be realigned.
Asset allocation is the deliberate split of a portfolio between different types of investments based on how much risk the investor is willing to take. Stocks, meaning shares of ownership in public companies, tend to grow faster but drop harder. Bonds, meaning loans you make to a government or company in exchange for regular interest payments and the return of the original amount at the end of a set term, tend to grow slower but hold steadier.
When stocks outperform bonds for a long period, the stock percentage grows automatically without any action by the investor, and the portfolio becomes riskier than originally intended. A 70/30 portfolio becomes 80/20, then 85/15, then something the investor never decided to own. Nothing broke and no bad decision was made. But the shape of the portfolio changed, and that change has real financial consequences because a more stock-heavy portfolio falls further during a market downturn than a balanced one.
Nick Maggiulli, author of Always Keep Buying and one of the most data-driven voices in personal finance, makes a compelling case that for investors still in the accumulation phase, meaning the years before retirement when you are still adding to your investments, simply buying more of whatever is underweight produces comparable outcomes to selling and rebalancing.
Think of it like topping up the shorter glass rather than pouring from the taller one. Same result, cleaner execution, and no bill from the IRS.
Why Rebalancing Is About Risk Not Returns
Most investors think rebalancing is about selling high and buying low in a disciplined systematic way. That framing is appealing and it is not the primary point. The real purpose of rebalancing is risk management, meaning keeping the portfolio at the level of volatility, meaning how much prices move up and down sometimes sharply in short periods, the investor originally agreed to accept.
When Jordan set her portfolio to 70/30, she was making a specific agreement with herself. She was saying I can handle this level of volatility and I want this level of protection if the market drops. When her portfolio drifted to 88/12, that agreement was quietly broken without any deliberate decision on her part. The right time to act is not when headlines suggest it but when drift has moved the portfolio away from that original agreement.
Take a pediatrician with the same 70/30 starting allocation. The agreement she made was based on a specific career timeline, a specific retirement target, and a specific tolerance for losses she could absorb without changing her plan. When that allocation drifts to 90/10 over a strong stock run, the loss exposure changes from a manageable 20 to 25 percent in a bad year to 35 to 40 percent in the same event. That is not a minor difference. Over a large portfolio it represents hundreds of thousands of dollars of unexpected loss at exactly the moment it is most difficult to absorb.
Research comparing different rebalancing thresholds consistently identifies five percentage points as the standard trigger. It represents the point where the risk management benefit of restoring balance meaningfully exceeds the transaction and tax cost of doing so. Tighter thresholds produce unnecessary activity. Wider thresholds allow drift that most investors never intended to carry.
When to Rebalance: The Only Framework You Need
The framework requires one rule and one optional addition. The rule is to rebalance when any asset class drifts more than five percentage points from its target weight. Jordan's 70 percent stock target triggers a rebalance when stocks reach 75 percent or fall to 65 percent, regardless of what the market has done recently or what any financial news cycle suggests.
The optional addition is a calendar layer. Review the portfolio once a year and also rebalance any time the five percent threshold is crossed between scheduled reviews. Dollar-cost averaging the contributions through this same period removes the timing question entirely, because new money flows toward the underweight asset on every scheduled deposit.
The trigger is always drift and nothing else. Not headlines, not instincts, not a feeling that things have moved significantly. Drift is a number and numbers are either above the threshold or below it.
That specificity is what separates a rebalancing system from a rebalancing intention, and most investors have the latter without ever building the former. Rebalancing is planned. Reacting feels planned. Most investors confuse those two things at exactly the moment the distinction matters most, which is when markets are moving dramatically and the impulse to do something is at its strongest.
How to Rebalance Without Creating a Tax Problem
Rebalancing inside tax-advantaged accounts, meaning accounts like a 401(k), traditional IRA, or Roth IRA where investments grow without being taxed each year, has no immediate tax consequences. Calculate the difference between rebalancing in a Roth, traditional, or taxable account before any sale, because the tax outcome can vary by thousands of dollars depending on which account holds the overweight position. Sell the overweight position, buy the underweight one, and the portfolio is restored at zero tax cost.
Rebalancing in a taxable brokerage account, meaning a standard investment account outside of retirement accounts where gains are taxed each year, is more complex. Selling an investment that has grown since it was purchased creates a capital gain, meaning the profit from selling something for more than it originally cost. The IRS taxes that profit at rates up to 23.8 percent for high earners, which can significantly reduce the benefit of rebalancing if it is not handled carefully.
The first tool before any selling is new contributions. Directing the next round of investments entirely into the underweight asset class moves the allocation back toward target without triggering any tax event. It is slower than selling but costs nothing and should always be the first approach in a taxable account.
The second tool is tax-loss harvesting, meaning the practice of selling positions worth less than their original purchase price to generate a loss that offsets gains elsewhere in the portfolio. Taxes matter more than the rebalancing itself for any portfolio large enough to produce a meaningful tax bill, which is why the order of operations matters as much as the threshold.
Only after both tools have been exhausted should selling appreciated positions in a taxable account be used as the primary rebalancing mechanism. Rebalancing should fix the portfolio's risk profile. It should not generate a tax bill that erases most of the benefit of having done it.
When to Do Nothing
There is a line from Buddhist philosophy that perfectly inverts the most common advice in the English language. Don't just do something, sit there. It sounds like a punchline. For investors watching their portfolio move during a volatile market, it is genuinely the most useful instruction available and one that most financial content never gives explicit permission to follow.
Most investors struggle not because they lack knowledge but because inaction during market movement feels like negligence even when it is the correct decision. Small movements in the portfolio feel significant and urgent. Most of them are neither. A two or three percentage point drift from the target allocation is within the normal range of market movement and does not warrant any transaction at all.
Doing nothing is the correct decision when the allocation is within five percentage points of target, when upcoming contributions in the next one to three months will naturally restore balance through addition rather than selling, and when the plan itself has not changed in any meaningful way. Delayed gratification is the single skill that compounds across every financial decision over decades, and resisting the impulse to act on small market movements is exactly the same muscle.
Most investors do not underperform because they failed to rebalance at precisely the right threshold. They underperform because they could not resist responding to movements that required no response and told themselves it was discipline.
Rebalancing follows a rule. Reacting follows a feeling. Only one of those compounds favorably over a thirty-year investment horizon and knowing the difference in a given moment is the entire skill.
THE BOTTOM LINE
• Rebalancing is not a return optimization strategy. It is a risk management tool that restores the portfolio to the volatility level originally chosen when drift has moved the allocation meaningfully away from target. A portfolio that drifts without correction quietly becomes something the investor never decided to own.
• Use a five percentage point threshold as the trigger. Check annually and act when the threshold is crossed between reviews. In taxable accounts direct new contributions to underweight assets first, and use tax-loss harvesting to offset gains before selling anything appreciated.
• Most of the time the correct move is no move. Don't just do something, sit there. Rebalancing follows a rule. Reacting follows a feeling. Knowing the difference is the entire skill.
Money Questions
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Rebalance based on drift rather than time, using a five percentage point threshold as the trigger: when any asset class moves more than five percentage points away from its target weight, the threshold has been crossed and action is warranted. Layer a calendar review on top by checking the portfolio once per year, but only act if the threshold has actually been crossed rather than rebalancing on a fixed schedule regardless of what the portfolio is doing. Most years the annual review will confirm that no action is needed, which is the correct outcome and not a sign that something was missed. This hybrid approach produces better risk-adjusted outcomes than pure calendar rebalancing because it responds to actual changes in portfolio risk rather than arbitrary dates.
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Not reliably, and expecting it to do so leads to the wrong decision framework for when and why to act. The primary purpose of rebalancing is risk management: restoring the portfolio to the volatility level and downside exposure the investor originally chose when the allocation has drifted meaningfully beyond that target. A secondary benefit is the occasional return improvement from systematically buying underperforming asset classes before they recover, but that benefit is inconsistent across different market environments and should not be the primary motivation for rebalancing. The consistent and reliable benefit is preventing a portfolio from becoming significantly more aggressive or conservative than intended without any deliberate decision having been made to change it.
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Start by rebalancing inside tax-advantaged accounts including 401ks and IRAs where trades produce no immediate tax consequences, executing any required corrections there before considering action in taxable accounts. In taxable brokerage accounts, direct new contributions toward underweight asset classes rather than selling overweight positions, which restores balance through addition at zero tax cost. If selling in a taxable account is ultimately necessary, identify any positions trading below their original purchase price and use those losses to offset the capital gains that selling appreciated positions would generate. Taxes matter more than achieving perfect allocation precision and the goal is to restore an acceptable risk profile at the lowest possible cost rather than hitting the exact target percentage regardless of the tax consequence.
By Karim Ali, MD, MBA. Emergency Physician & Finance Educator