If you set up an investment portfolio a few years ago with a specific mix of stocks and bonds, there's a good chance that mix looks quite different today, simply because different assets grow at different rates over time. Rebalancing is the process of bringing your portfolio back to your original target allocation, and while it sounds like a minor maintenance task, it has real implications for your risk level and long-term returns that are worth understanding clearly.
When you first build a portfolio, you typically choose a target allocation – say, 70% stocks and 30% bonds – based on your risk tolerance, timeline, and goals. Over time, as stocks and bonds grow at different rates, that allocation naturally drifts. If stocks have a strong multi-year run, your portfolio might drift to 80% stocks and 20% bonds without you making a single trade, simply because the stock portion grew faster than the bond portion.
Rebalancing means selling a portion of the asset class that's grown to become overweight and buying more of the one that's become underweight, bringing your allocation back toward your original target percentages.
The core purpose of rebalancing isn't to boost returns directly – it's to manage risk by keeping your portfolio's actual risk level aligned with what you originally intended, rather than letting market movements silently shift your risk exposure without you noticing. A portfolio that's drifted from 70% to 85% stocks is carrying meaningfully more risk than you may have originally signed up for, even though you haven't made any active decisions to increase that risk yourself.
Why this matters practically: if a market downturn hits while your allocation has drifted more heavily into stocks than you intended, you'll experience a larger loss than your original risk tolerance was designed to handle, simply because the drift happened gradually and went unaddressed.
For most long-term investors using a diversified portfolio, yes, rebalancing periodically is generally considered a sound practice, though the specific frequency and method involve some genuine flexibility rather than a single correct answer. If you're invested in a target-date fund or an automatically managed robo-advisor portfolio, rebalancing is typically handled for you automatically, and you may not need to do anything manually at all.
If you manage your own portfolio directly – individual stock and bond funds, or a self-directed brokerage account – rebalancing becomes something you need to actively initiate, and this is where many investors either forget entirely or feel uncertain about how and when to do it.
A calendar-based approach involves rebalancing at fixed intervals – annually or semi-annually is common – regardless of how much your allocation has actually drifted at that point. This is simple to follow and doesn't require constant monitoring, though it can mean rebalancing even when drift is minor, or missing a period where significant drift occurred between scheduled check-ins.
A threshold-based approach instead involves rebalancing whenever an asset class drifts beyond a certain percentage from its target – for example, rebalancing whenever any allocation moves 5 percentage points or more away from its intended target. This requires more regular monitoring but can be more responsive to actual market movements rather than an arbitrary calendar date.
Rebalancing in a taxable brokerage account can trigger capital gains taxes when you sell appreciated assets to bring your allocation back in line, which is a real cost worth factoring into your decision, particularly for accounts held outside of tax-advantaged retirement accounts like a 401(k) or IRA. Within tax-advantaged retirement accounts, this concern doesn't apply, since trades within those accounts generally don't trigger immediate tax consequences.
There's also a psychological dimension worth being honest about: rebalancing often means selling some of what's been performing well and buying more of what's underperformed recently, which can feel counterintuitive even though it's the entire point of the strategy – maintaining your intended risk level rather than chasing whatever's currently outperforming.
Check your portfolio's actual allocation at least once a year, comparing it against your original target, even if you decide not to rebalance every single time you check. If you're using a taxable account, consider directing new contributions toward your underweight asset class first, since this can accomplish some rebalancing without triggering a taxable sale of appreciated assets.
For retirement accounts specifically, rebalancing more frequently carries less downside since there's no immediate tax consequence, making a threshold-based or even more frequent calendar-based approach more reasonable in these accounts specifically compared to taxable accounts. If you're using a target-date fund or robo-advisor, confirm directly whether rebalancing is handled automatically, since this varies by provider and account type, rather than assuming it's happening without checking.
Rebalancing doesn't guarantee higher returns, and in some periods, an unrebalanced, drifted portfolio might even outperform a regularly rebalanced one, particularly during a sustained bull market in whichever asset class has become overweight. The value of rebalancing is primarily about managing risk consistency with your actual goals and timeline, not about maximizing returns in any specific market environment, and it's not a strategy that eliminates investment risk or guarantees a particular outcome.
How often should I rebalance my portfolio? Common approaches range from annually to whenever an allocation drifts a set percentage from target, and there's no single correct frequency – the right choice depends on your account type, tax situation, and how actively you want to manage the process.
Does rebalancing cost money? In a taxable account, it can trigger capital gains taxes on sold assets, while in tax-advantaged retirement accounts, rebalancing generally doesn't have the same immediate tax consequence.
Is rebalancing necessary if I use a target-date fund? Usually not manually, since target-date funds are specifically designed to handle rebalancing automatically as part of their structure, though it's worth confirming this directly with your specific fund's documentation.
Rebalancing is less about chasing better returns and more about making sure your portfolio's actual risk level still matches what you originally intended, since markets drift your allocation over time without you making a single active decision. Understanding your account type and the tax implications involved helps you decide an approach that fits your specific situation.
U.S. Securities and Exchange Commission: Investor Bulletin on Rebalancing – https://www.sec.gov/investor
Vanguard: Principles of Portfolio Rebalancing – https://investor.vanguard.com/investor-resources-education/
IRS: Capital Gains and Losses – https://www.irs.gov/taxtopics/tc409
