Rebalancing a Portfolio: When to Do It and How
Portfolio drift can quietly change your risk profile. Learn when and how to rebalance to keep your investments on track.
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Key Takeaways
- Portfolio drift occurs when asset returns shift your actual allocation away from your target.
- Rebalancing restores your intended risk level by selling overweight assets and buying underweight ones.
- Common triggers include a threshold breach of 5 percentage points or a scheduled calendar review.
- Tax-advantaged accounts are generally the most efficient place to rebalance without triggering capital gains.
- Rebalancing too frequently can increase transaction costs without meaningfully improving outcomes.
Why portfolios drift and why it matters
When you first set an asset allocation, you choose a mix designed to match your risk tolerance and time horizon. Over time, different asset classes grow at different rates. A strong run in equities, for instance, can push stocks from 60% of your portfolio to 70% or more without you buying a single additional share. This is portfolio drift.
Drift changes your actual risk exposure. A portfolio that has shifted heavily toward stocks carries more volatility than your original plan intended. If markets fall sharply, you may experience larger losses than you built your retirement plan around. Understanding asset allocation fundamentals is the starting point for knowing what your target should be in the first place.
Rebalancing is the process of selling assets that have grown above target weight and buying those that have fallen below it. The goal is not to maximize returns in any single period. It is to keep your risk profile consistent with your long-term plan.
This article is general information, not personal advice
The steps below describe how portfolio rebalancing works as a general practice. They are not tailored to your individual tax situation, risk tolerance, or financial goals. Consult a licensed financial adviser or tax professional before making changes to your portfolio.
What you need before you start
Effective rebalancing requires a few things in place before you execute any trades.
What you will need
Current account statements
Shows the present market value of each holding so you can calculate your actual allocation.
Investment policy statement or target allocation record
Documents your intended allocation percentages so you have a clear benchmark to compare against.
Spreadsheet or portfolio tracking tool
Calculates drift from target and the trade sizes needed to restore balance.
Tax records or cost-basis information
Identifies which lots carry embedded gains or losses relevant to decisions in taxable accounts.
One common pitfall worth noting: spending growth can quietly erode the savings base you are trying to protect. If you have not reviewed your savings rate recently, the article on how lifestyle creep affects retirement savings covers how gradual spending increases can offset investment discipline over time.
Step-by-step rebalancing process
Follow these steps in order. The process typically takes between 20 and 60 minutes, depending on how many accounts you hold and whether you need to research tax implications.
Record your current allocation
Pull up your most recent account statements for every account in your portfolio. For each account, list the current market value of each holding. Sum the values by asset class (domestic stocks, international stocks, bonds, cash) across all accounts, then divide each total by your overall portfolio value to get the current percentage weight of each class.
Compare against your target allocation
Place your current percentages next to your target percentages for each asset class. The difference between the two is called drift. For example, if your target is 60% stocks but markets have pushed stocks to 68%, you have an 8 percentage point overweight in stocks.
A drift of 5 percentage points or more from target is a common threshold many investors use to trigger a rebalance. Some use 10 percentage points. The right threshold depends on your tolerance for tracking error and your sensitivity to transaction costs and taxes.
Decide where to execute the trades
Before calculating trade sizes, identify which accounts to use. Tax-advantaged accounts (traditional 401(k), Roth IRA, traditional IRA) allow you to buy and sell without triggering a taxable event in the year of the trade. Rebalancing inside these accounts is generally more straightforward.
In taxable brokerage accounts, selling an appreciated position creates a realized capital gain. Holding a position for more than one year qualifies for long-term capital gains rates, which are lower than ordinary income rates for most taxpayers. If possible, concentrate your selling activity in tax-advantaged accounts and use new contributions or dividends to adjust taxable accounts.
Calculate the trades needed
Determine the dollar amount to move in each asset class. Multiply your total portfolio value by the difference between your target weight and current weight for each class.
Example: if your portfolio is worth $200,000 and stocks are 8 percentage points overweight, you need to reduce stocks by approximately $16,000 ($200,000 x 0.08). That same $16,000 would then be moved into underweight asset classes, proportionally, to restore the target mix.
Execute the trades and confirm
Place the sell orders for overweight assets first, then place the buy orders for underweight assets once the proceeds settle (settlement typically takes one to two business days for most securities in the U.S.). After trades settle, recalculate your allocation to confirm you are within acceptable range of your target.
Keep a record of the trades you made, the prices, and the date. This documentation matters for tax reporting and for your own review at the next rebalancing interval.
Set your next review date
Decide on a rebalancing schedule going forward. Two common approaches are calendar-based (review quarterly or annually regardless of drift) and threshold-based (review only when drift exceeds a set percentage). Many investors combine both: check annually and also check whenever you see significant market movement.
Record the date of this rebalance and your post-rebalance allocation as a baseline for the next review.
Use new contributions to rebalance passively
If you are still in the accumulation phase, directing new contributions toward underweight asset classes can restore your target allocation without selling anything. This approach avoids transaction costs and, in taxable accounts, sidesteps capital gains entirely.
Rebalancing in taxable accounts has tax consequences
Selling appreciated assets in a taxable brokerage account may generate capital gains, which are subject to federal and potentially state income tax. Factor in your tax situation before executing trades outside tax-advantaged accounts. A tax professional can help you evaluate the cost.
Common misconceptions about rebalancing
Rebalancing is sometimes misunderstood as a way to improve returns by selling winners and buying losers. It does not reliably do that. Its actual function is risk control, not performance enhancement. Past performance of any asset class does not guarantee future results, and rebalancing into an underperforming asset class may feel counterintuitive even when it is consistent with your plan.
A related misconception is that a buy-and-hold approach without rebalancing is inherently safer. It is not. An unrebalanced portfolio can drift far outside your intended risk parameters, as explored in the broader discussion of investing misconceptions that affect retirement savers.
Another common error is rebalancing every account in isolation rather than treating the full portfolio as a single unit. If you hold bonds in your IRA and stocks in your 401(k), the allocation that matters is the combined picture across both accounts.
This article is for informational purposes only and does not constitute personalized investment, tax, or legal advice. Consult a qualified financial adviser or tax professional regarding decisions specific to your situation.
Investing Basics Editorial Team
Investing Basics Editorial Team is the collective byline for our editorial team and contributor network. Articles published under this byline or an editorial pen name are researched, written, and reviewed according to our editorial standards for clarity, consistency, and independence before publication.
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