How to rebalance your portfolio without guessing at the market

The market will happily rewrite your portfolio while you sleep. It will not ask permission.

Suppose you chose a mix of 70% stocks and 30% bonds because it fit your goal, time horizon, and tolerance for market declines. After a strong run for stocks, the portfolio reaches 76% stocks and 24% bonds. You did not make a new decision to accept more stock-market risk. The winners simply took up more room.

That is drift wearing a nice return.

Rebalancing is the process of returning a portfolio to its intended asset allocation. It is not a prediction that the winner is about to fall or the laggard is about to recover. It is maintenance: compare what you own with the plan you chose, then correct a meaningful difference.

The arithmetic is not the hard part. The hard part is deciding in advance what will trigger action, which accounts to use, and how to avoid unnecessary taxes and trading.

The short version: Write down a target allocation for the whole goal, not just one account. Review it on a schedule you can keep. Rebalance only when your rule says to act, using new contributions, distributions, or withdrawals before selling when practical. Check taxes, fees, and trading restrictions before placing an order. If your goal or ability to take risk has changed, choose a new target deliberately instead of calling the change a rebalance.

Rebalancing starts with a target

You cannot measure drift without a destination. A target allocation states what percentage of the portfolio belongs in each broad asset category, such as U.S. stocks, non-U.S. stocks, bonds, and cash.

The appropriate mix depends on the goal. The SEC’s guide to asset allocation, diversification, and rebalancing identifies time horizon and risk tolerance as central considerations. Money needed soon generally has less time to recover from a market loss than money intended for a goal decades away.

Use one target for each distinct goal. A retirement portfolio and a house down-payment fund do not need to share an allocation merely because the same person owns them.

Also distinguish three related jobs:

• Asset allocation divides money among categories such as stocks, bonds, and cash.
• Diversification spreads money across investments within and among those categories.
• Rebalancing restores the chosen percentages after market movement, contributions, or withdrawals change them.

Rebalancing can maintain a diversified plan, but it cannot repair a weak plan automatically. Returning to 100% in one company stock is still concentrated. Before writing a rule, run a portfolio x-ray for overlap and missing exposures.

Three workable rebalancing rules

There is no single trigger that fits every investor. The important step is to choose a rule before headlines or emotions make the decision for you.

Investor.gov describes both calendar- and threshold-based approaches and notes that rebalancing generally works best when done relatively infrequently. Vanguard’s current rebalancing guide presents the same three methods and says an annual rebalance is practical for many investors.

I like a rule that fits on an index card:

Every November, I will review the allocation for this goal. I will rebalance if any major asset category is at least 5 percentage points away from its target. I will first direct available contributions and cash flows to underweight categories. If trades are still required, I will check taxes, fees, and account restrictions before selling.

Five percentage points is an illustration, not a universal recommendation. A narrower band keeps the portfolio closer to target but may require more trading. A wider band permits more drift. The suitable choice depends on the portfolio, account types, trading costs, tax situation, and how tightly the risk level needs to be controlled.

Measure drift in percentage points

Use percentage points, not percent change, when comparing an allocation with its target.

If stocks move from a 70% target to 76% of the portfolio, they are 6 percentage points overweight. Saying the allocation increased by about 8.6% answers a different question and makes a rebalancing rule harder to apply.

For each category:

1. Add its value across every account assigned to the goal.
2. Divide that value by the total portfolio value.
3. Subtract the target percentage from the current percentage.

At the current $120,000 balance, a 70/30 target equals $84,000 in stocks and $36,000 in bonds. A full rebalance using sales and purchases would move $7,200 from stocks to bonds, before considering market movement, taxes, fees, or order execution.

The calculation is:

target dollars = total portfolio value × target percentage

Do not create a false level of precision. Prices move, mutual funds may price only once each business day, and deposits may arrive after the calculation. The goal is to restore the intended risk mix, not to keep every category on target to the penny.

Four ways to restore the target

The SEC’s guide identifies three basic methods: sell from overweight categories and buy underweight ones, add new money to underweight categories, or redirect continuing contributions. A fourth practical method for investors taking money out is to withdraw from overweight categories.

1. Direct new contributions

This is often the cleanest first step for someone still saving. Send 401(k), IRA, or brokerage contributions toward the underweight category until the allocation returns to its permitted range.

In the example above, adding $10,000 entirely to bonds would produce a $130,000 portfolio with $91,200 in stocks and $38,800 in bonds. That is about 70.2% stocks and 29.8% bonds—very close to the 70/30 target—without selling anything.

This method becomes less powerful as the portfolio grows relative to new contributions. A $500 monthly contribution can correct a small drift in a $20,000 account much faster than in a $1 million portfolio.

2. Redirect cash distributions

Instead of automatically reinvesting every dividend or interest payment into the investment that produced it, available cash can be directed toward underweight categories. The amounts may be modest, but this approach can reduce the size of later trades.

Changing dividend-reinvestment settings has operational and possible tax details that vary by account and provider. Confirm how the account handles cash, settlement, and purchases before relying on the method.

3. Use withdrawals

An investor already spending from a portfolio can take planned withdrawals from overweight categories. This simultaneously funds spending and moves the remaining portfolio toward target.

Required distributions, taxes, and account-specific withdrawal rules can complicate the choice. Treat the withdrawal plan and rebalancing plan as one system rather than making two unrelated sets of trades.

4. Sell and buy

When cash flows are not enough, sell part of an overweight investment and purchase the underweight category. In a tax-advantaged retirement account, the trade generally does not create the same current capital-gains issue as a sale in a taxable brokerage account, although account rules and other tax consequences can still matter.

In a taxable account, selling an investment for more than its adjusted basis generally creates a capital gain. The IRS explains the basic calculation and reporting framework in Topic No. 409, Capital Gains and Losses. Cost basis, holding period, losses, income, and the specific security lots sold can affect the result. Review those details or consult a tax professional before trading. Do not let a rebalancing spreadsheet make a tax decision by accident.

Look across accounts before trading inside one

An account can appear unbalanced while the portfolio for the goal is on target.

Suppose a workplace plan holds mostly bonds because it offers a strong low-cost bond option, while an IRA holds mostly stock funds. Rebalancing each account to 70/30 could add unnecessary trades and duplicate holdings. If both accounts serve the same retirement goal, first measure them together.

Use a simple inventory:

Then total each category across the accounts. This view may reveal that the least disruptive trade belongs in a retirement account, or that new workplace contributions can fix drift without touching a taxable holding.

Do not combine accounts simply because they are all investments. Accounts meant for different goals can require different targets, deadlines, and risk levels.

A rebalance is not the same as changing the plan

Rebalancing returns to an existing target. Changing the target is a new asset-allocation decision.

A new target may be reasonable when:

• the spending date is closer;
• the amount or purpose of the goal has changed;
• income, job stability, debt, or emergency reserves have changed materially;
• the investor has learned that the existing level of volatility is not tolerable; or
• the original allocation was never tied to a clear goal.

It is not a disciplined target change to increase stocks because stocks recently rose, move entirely to cash after a decline, or chase whichever category has the best recent return. Investor.gov specifically warns against changing an allocation merely because of the relative performance of asset categories.

If choosing and maintaining a changing retirement allocation is the main obstacle, a target-date fund may be worth researching. Investor.gov explains that these funds typically adjust their mix and become more conservative as the target date approaches. They are not interchangeable: funds with the same date can have different strategies, risks, glide paths, holdings, and fees, and they do not guarantee adequate retirement income.

A 20-minute annual rebalancing review

Use this checklist on the date written into your rule:

1. Confirm the goal. Has the deadline, amount, or purpose changed?
2. Confirm the target. Is the current target still appropriate for the goal and risk tolerance?
3. List every account. Include all accounts and holdings assigned to the goal.
4. Group the holdings. Classify them consistently into the asset categories used by the target.
5. Calculate current percentages. Divide each category’s value by the portfolio total.
6. Apply the trigger. Trade only if the written calendar or threshold rule calls for it.
7. Use cash flows first. Consider contributions, distributions, and planned withdrawals.
8. Check friction. Review taxes, cost basis, fees, spreads, settlement, and account restrictions.
9. Place the minimum necessary trades. Correct the allocation without redesigning the entire portfolio.
10. Record the result. Save the date, values, target, action, and the next scheduled review.

Also check whether a provider or employer plan already performs some rebalancing automatically. Do not layer manual trades onto an automated service without understanding how the two systems interact.

The bottom line

Rebalancing is maintenance, not prophecy. Start with a target tied to a real goal. Choose a calendar, threshold, or combined rule. Measure the whole portfolio, then use the least disruptive method that restores the intended allocation.

The practical next step is to write one sentence: “I will review this portfolio on ___ and rebalance when ___.” Add the target percentages and the accounts included. That small policy turns a vague intention into a decision you can follow when markets are calm or chaotic.

This article provides general educational information, not individualized investment, tax, legal, or financial advice or a recommendation to buy, sell, or hold any security. Investments can lose value. Rebalancing and diversification do not guarantee a profit or prevent every loss. Tax rules, account terms, costs, and investment options can change. Verify current sources and consider qualified professionals who can evaluate your complete circumstances before acting.

Sources reviewed November 2, 2026

• SEC Investor.gov: Beginners’ Guide to Asset Allocation, Diversification, and Rebalancing
• SEC Investor.gov: Target Date Funds
• Internal Revenue Service: Topic No. 409, Capital Gains and Losses
• Vanguard: Rebalancing your portfolio