How to Rebalance a Portfolio Once a Year

Rebalancing sounds like something only professional money managers do, but it's really just a maintenance task — similar to rotating tires. Over time, some investments in your portfolio grow faster than others, and your original mix of stocks, bonds, and other assets drifts away from your intended target. Rebalancing simply means selling a bit of what's grown and buying more of what hasn't, to restore your original plan.

Doing this once a year is enough for most long-term investors. This article covers why drift happens, how to check your current allocation, and a simple step-by-step process for rebalancing without overthinking it.

Why portfolios drift in the first place

Suppose you start with a target of 70% stocks and 30% bonds. If stocks have a strong year and bonds are flat, your portfolio might naturally shift to 78% stocks and 22% bonds without you doing anything at all — simply because the stock portion grew faster. That drift isn't necessarily bad in a rising market, but it does mean your portfolio is now riskier than you originally intended, since more of your money is exposed to the more volatile asset.

Why rebalancing matters

Without rebalancing, portfolios tend to drift toward whatever has been performing best recently, which is the opposite of a disciplined strategy — you end up increasingly concentrated in an asset right as it may be getting more expensive relative to fundamentals. Rebalancing forces a small, systematic version of "buy low, sell high": you trim the portion that's grown and add to the portion that's lagged, based on your predetermined targets rather than a guess about what will do well next.

How often should you actually do it?

Research and industry practice both suggest that rebalancing too frequently (like monthly) adds transaction costs and tax consequences without meaningfully improving returns, while rebalancing too rarely (like never) lets risk drift too far from your target. Once a year is a widely used middle ground — frequent enough to keep your risk level in check, infrequent enough to avoid excessive trading and to fit easily into a yearly financial check-up.

A step-by-step approach

Step 1: Pick a consistent date

Choose a recurring date — your birthday, the start of the year, or the day after you file taxes — and put a reminder in your calendar. Consistency matters more than the specific date you choose.

Step 2: Calculate your current allocation

Add up the current dollar value of each asset class across all your accounts (don't forget old 401(k)s and IRAs) and calculate each one's percentage of your total portfolio.

Step 3: Compare against your target

Most advisors suggest a rebalancing "trigger" of about 5 percentage points of drift — for example, if your bond target is 30% and it has drifted to 24% or 36%, that's typically considered enough drift to act on. Smaller drifts often aren't worth the trading effort or any tax consequences.

Step 4: Make the trades

Sell enough of the overweight asset and buy enough of the underweight one to bring the portfolio back to target. In tax-advantaged accounts like a 401(k) or IRA, this creates no tax bill. In a taxable brokerage account, selling appreciated investments can trigger capital gains tax, so where possible, rebalance using new contributions or dividends first before selling existing holdings.

Sample rebalancing check (illustrative)

Asset class	Target	Current (after 1 year)	Drift	Action
U.S. stocks	50%	57%	+7 pts	Trim
International stocks	20%	19%	-1 pt	Hold
Bonds	30%	24%	-6 pts	Add

Rebalancing isn't about predicting the market — it's about refusing to let last year's winners quietly redefine your risk.

Using new money instead of selling

If you're still contributing regularly, you can often rebalance simply by directing new contributions toward whichever asset class has fallen below target, rather than selling anything. This is typically the most tax-efficient way to rebalance a taxable account, since it avoids realizing any capital gains, and many workplace retirement plans let you set contribution allocations by asset class to automate part of this process.

Don't forget accounts you might overlook

A full rebalancing check should include every investment account you hold, not just your primary brokerage account. Old 401(k)s from previous employers, a spouse's retirement accounts, a health savings account invested in funds, and even a taxable brokerage account you rarely check can all shift your true overall allocation without your noticing. Treat your household's total invested assets as one combined portfolio when calculating percentages, rather than rebalancing each account in isolation, since that gives a more accurate picture of your actual risk exposure.

Finally, resist the urge to rebalance reactively during a sharp market move. A once-a-year schedule is meant to remove emotion from the process; making extra ad-hoc trades every time the market drops or spikes usually adds cost and stress without improving long-term results.

Rebalancing inside a target-date fund

If most of your retirement money sits in a single target-date fund, the fund manager already handles rebalancing automatically behind the scenes, gradually shifting the mix toward more bonds as the target date approaches. In that case, your own annual check is mostly about confirming you don't hold duplicate, conflicting allocations elsewhere — for example, a separate individual stock position that quietly skews your overall risk far higher than the target-date fund alone would suggest.

What to do next

• Set a recurring annual calendar reminder for a specific rebalancing date.
• On that date, list every account and asset class, calculate current percentages, and compare them to your target allocation.
• Rebalance by directing new contributions toward underweight assets first, and only sell existing holdings in taxable accounts if drift is significant and the tax impact is manageable.

Informational only — not financial advice.