Rebalancing means selling investments that have grown and buying ones that have fallen behind to keep your portfolio in the mix you originally chose

When you first build an investment portfolio, you decide how much money goes into stocks, bonds, and other assets — say 60% stocks and 40% bonds. Over time, stocks often grow faster than bonds. After a year or two, your portfolio might drift to 70% stocks and 30% bonds without you doing anything. Rebalancing is the act of selling some of those stocks and buying bonds to get back to 60/40. It forces you to sell high and buy low, which is the opposite of what most people do naturally.

The reason this matters is that your original mix was designed for your age, risk tolerance, and time horizon. When your portfolio drifts, you are taking on more risk than you intended. A portfolio that has drifted to 70% stocks is more volatile and more likely to lose money in a downturn than the 60/40 mix you chose. Rebalancing keeps you on track toward your actual financial goal instead of letting market momentum push you into a riskier position.

Key Takeaways

  • Rebalancing means selling investments that have grown and buying ones that have fallen behind to return to your target allocation.
  • Without rebalancing, a rising stock market will gradually shift your portfolio to hold more stocks and less bonds than you planned, increasing your risk.
  • Most people rebalance once a year or when any asset class drifts more than 5 percentage points from its target, whichever comes first.
  • Rebalancing costs money in taxes and trading fees, so doing it too often can erase the benefit; doing it too rarely defeats the purpose.
  • Automatic rebalancing through a robo-advisor or target-date fund handles this for you, though you pay a fee for the service.

How drift happens and why it matters

Drift occurs because different asset classes grow at different rates. Stocks historically return about 10% per year on average, while bonds return about 5%. If you start with $100,000 split 60/40, after one year of average returns you have roughly $106,000 in stocks and $102,000 in bonds — a total of $108,000. Your stock portion is now 61.1% instead of 60%. This seems small, but over five or ten years the drift becomes large.

The problem is that drift always happens in the direction of whatever is performing best. In a bull market, stocks pull ahead and your portfolio becomes too aggressive. In a bear market, bonds hold up better and your portfolio becomes too conservative. Either way, you end up with a different risk level than you chose. If you are five years from retirement and your portfolio has drifted to 75% stocks because of a long bull market, a sudden crash could wipe out years of savings right when you need the money most.

Rebalancing also forces a discipline that most investors lack: selling winners and buying losers. When stocks are soaring, it feels wrong to sell them. When bonds are flat or falling, it feels wrong to buy more. But that discipline is what separates people who stick to a plan from people who chase performance and end up buying high and selling low.

How often to rebalance and what triggers a rebalance

There is no single correct answer, but most financial advisors suggest one of two approaches: rebalance on a calendar schedule (once a year, or quarterly) or rebalance when drift exceeds a threshold (usually 5 percentage points). A 60/40 portfolio would trigger a rebalance if stocks rose to 65% or fell to 55%. Many people use both: rebalance annually, but also rebalance immediately if drift exceeds the threshold.

Calendar-based rebalancing is simpler and works well for most people. Once a year — often at tax time or on your birthday — you check your allocation and rebalance if needed. This approach is predictable and keeps you from obsessing over your portfolio. Threshold-based rebalancing is more active and responds to market moves, but it requires you to check your portfolio regularly and can lead to more frequent trading.

The right frequency depends on your situation. If you are young and have decades until retirement, annual rebalancing is usually enough. If you are close to retirement or have a large portfolio, more frequent rebalancing may make sense. If you have a small portfolio under $10,000, rebalancing costs (trading fees and taxes) may outweigh the benefit, so you might rebalance only every two or three years.

The cost of rebalancing: taxes and trading fees

Every time you sell an investment, you may owe capital gains tax on the profit. If you have held a stock for more than a year, the tax rate is usually lower (long-term capital gains), but it is still a real cost. In a taxable brokerage account, rebalancing too often can create a large tax bill. In a retirement account like a 401(k) or IRA, there is no tax on the sale, so rebalancing is free from a tax perspective.

Trading fees have fallen sharply over the past decade — most brokers now charge zero commission on stock and ETF trades — but they are not zero everywhere. Some funds charge a fee when you buy or sell, and some advisors charge a percentage of assets under management. If you rebalance quarterly and pay $10 per trade, that is $40 per year on a small portfolio, which can be significant.

The math is simple: rebalancing has a cost, so you want to rebalance often enough to keep your risk on track but not so often that fees and taxes eat the benefit. For most people in retirement accounts, annual rebalancing strikes the right balance. For taxable accounts, you might rebalance less often or use tax-loss harvesting (selling losers to offset gains) to reduce the tax hit.

Rebalancing through target-date funds and robo-advisors

If you do not want to rebalance manually, two common options handle it for you. A target-date fund is a single mutual fund or ETF that holds a mix of stocks and bonds and automatically rebalances as you get older. You pick the fund based on your expected retirement year — for example, a 2050 target-date fund if you plan to retire around 2050 — and the fund manager adjusts the allocation over time, gradually shifting from aggressive to conservative.

A robo-advisor is an online service that builds a portfolio for you based on a questionnaire, then automatically rebalances it on a set schedule (usually quarterly or annually). Robo-advisors typically charge 0.25% to 0.50% per year in fees, which is lower than a human financial advisor but higher than managing your own portfolio. They work well if you want a hands-off approach and do not mind paying for automation.

The trade-off is simplicity versus control. With a target-date fund or robo-advisor, you do not have to think about rebalancing, but you also have less say in exactly what investments you own. If you want to hold specific stocks or bonds, or if you want to time your rebalancing for tax reasons, manual rebalancing gives you that control.

Rebalancing in different market conditions

In a rising market, rebalancing forces you to sell stocks (the winners) and buy bonds (the laggards). This feels counterintuitive because stocks are performing well, but it is exactly what you should do. You are locking in gains and moving money into assets that are likely to perform better in the future. If the market crashes the next month, you will be glad you did.

In a falling market, rebalancing forces you to sell bonds and buy stocks. Again, this feels wrong — stocks are falling, so why buy more? But stocks are now cheaper, and your bond holdings have held their value. Rebalancing moves money from what is working (bonds) to what is not (stocks), positioning you to benefit when stocks recover. This is the essence of buying low.

The hardest time to rebalance is during extreme volatility, when markets are swinging wildly and every decision feels urgent. This is precisely when you should stick to your plan and rebalance on schedule. Emotional decisions made during panic or euphoria are usually wrong. A disciplined rebalancing schedule removes emotion from the equation.

Rebalancing with new contributions and withdrawals

If you are still working and adding money to your portfolio each month, you can use those contributions to rebalance without selling anything. If your portfolio is overweight in stocks and underweight in bonds, direct your new contributions to bonds until the allocation is back on track. This is called "rebalancing through contributions" and it avoids trading costs and taxes.

If you are retired and taking withdrawals, you can rebalance by withdrawing from the asset class that is overweight. If stocks have grown to 70% of your portfolio and you need to withdraw $10,000, take it from stocks. This brings your allocation closer to your target without buying anything.

Both of these approaches work only if your contributions or withdrawals are large enough to make a difference. If you are adding $200 per month but your portfolio is $500,000, the contributions will not move the needle much. In that case, you still need to rebalance by buying and selling.

Frequently Asked Questions

What if I rebalance and the market immediately goes the other way?

That happens sometimes, and it is frustrating. You sell stocks to buy bonds, then stocks soar. But over long periods, rebalancing works because you are buying low and selling high on average. One bad trade does not mean the strategy is wrong. Stick to your schedule and trust the process.

Do I have to rebalance if my portfolio is only slightly off target?

No. If your target is 60/40 and you are at 61/39, rebalancing is probably not worth the cost. Most advisors suggest a 5 percentage point threshold — rebalance when you drift to 65/35 or 55/45. This balances the benefit of staying on track against the cost of trading.

Is rebalancing the same as diversification?

No. Diversification means holding different types of investments so that losses in one area are offset by gains in another. Rebalancing is the act of maintaining that diversification over time. You diversify once when you build your portfolio; you rebalance regularly to keep that diversification intact.

Should I rebalance my 401(k) differently than my taxable brokerage account?

Yes. In a 401(k) or IRA, there is no tax on sales, so you can rebalance as often as you want without a tax bill. In a taxable account, taxes matter, so you might rebalance less often or use new contributions to rebalance instead of selling. Some people rebalance their retirement accounts quarterly and their taxable accounts annually.

What if one investment has lost a lot of money — should I still rebalance into it?

Yes, if it is part of your plan. Rebalancing means buying what is down, which is hard psychologically but correct mathematically. If a bond fund has fallen because interest rates rose, bonds are now more attractive, and rebalancing into them positions you for better returns when rates fall. Do not confuse a temporary loss with a bad investment.