Rebalancing Your Portfolio: When and How Often

Investing · 7 min read

You choose an allocation of 70% stocks and 30% bonds. Two years later, stocks have run and you are holding 82% stocks. You did not decide to take more risk — the market decided for you. Rebalancing is the act of taking that decision back.

Why Drift Is a Problem

Drift is not a technicality. It systematically increases risk precisely when risk is most expensive. Portfolios drift toward whatever has performed best, meaning your exposure to an asset class peaks after it has already risen and troughs after it has already fallen.

An investor who chose a 60/40 split a decade ago and never rebalanced would have entered subsequent downturns with a considerably higher equity weight than intended, and taken losses larger than the plan called for. The allocation you wrote down stops describing the portfolio you own within a year or two.

How Rebalancing Works

Sell some of what has grown beyond its target, buy what has fallen below it, and return to the intended weights. Mechanically simple. Emotionally uncomfortable, because it always means trimming your winners and adding to your losers.

Asset	Target	Current value	Current weight	Action
U.S. stocks	50%	$62,000	56%	Sell about $7,000
International stocks	20%	$21,000	19%	Buy about $1,000
Bonds	30%	$27,000	25%	Buy about $6,000
Total	100%	$110,000	100%	Back to target

Note what this accomplishes without any forecast: it sold high and bought low, entirely as a byproduct of following a rule.

Two Approaches

Calendar rebalancing checks the portfolio on a fixed schedule — annually is the most common and generally sufficient. It is simple, requires no monitoring, and works well for anyone who would rather not think about it.

Threshold rebalancing acts when any asset class drifts more than a set amount from target, commonly five percentage points in absolute terms or 25% in relative terms. It responds to actual market movement rather than the calendar, which means it acts during volatile periods when rebalancing has the most value and stays quiet during calm ones.

The hybrid most practitioners settle on: check once or twice a year, and rebalance only if something has drifted past your threshold. This avoids both constant tinkering and years of neglect.

Rebalance With New Money First

If you are still contributing, most rebalancing can happen without selling anything. Direct new contributions toward whichever asset class is underweight. In a growing portfolio, this alone often keeps allocations close to target for years.

In retirement, the reverse applies: take withdrawals from whatever is overweight. Both approaches avoid transaction friction and, in taxable accounts, avoid triggering gains.

The Tax Dimension

Inside a 401(k), IRA, or other tax-advantaged account, rebalancing has no tax consequences. Sell and buy as your rule dictates.

In a taxable account, selling appreciated assets realises capital gains. Several tactics reduce the cost: rebalance primarily inside tax-advantaged accounts while treating all your holdings as one combined portfolio, direct dividends and new contributions to underweight assets, harvest losses when available to offset gains, and prefer selling lots held more than a year to qualify for long-term rates.

If a rebalance in a taxable account would trigger a large gain, widening your threshold is often the better answer. The tax bill is certain; the benefit of a precise allocation is not.

Does Rebalancing Increase Returns?

This is frequently oversold. The primary and reliable benefit of rebalancing is risk control — keeping the portfolio volatility and drawdown profile close to what you signed up for. Return effects are situational.

In markets that oscillate, rebalancing can add modest return by systematically buying declines. In markets with long sustained trends, rebalancing away from the winning asset reduces return compared with letting it ride. Over long periods with mixed conditions the return effect is small and can go either way. The risk effect, by contrast, is consistent, and it is the real reason to do it.

Practical Rules Worth Adopting

Pick one method — annual, threshold, or the hybrid — and write it into your plan so the decision is already made
Use new contributions as the first rebalancing tool before selling anything
Look at all accounts together as a single portfolio rather than balancing each one separately
Keep the underlying funds broad, since rebalancing cannot fix a portfolio built from overlapping narrow bets
Ignore small deviations, because rebalancing for a two-point drift creates costs without meaningful benefit
Record the date and the resulting weights each time, so next year starts from facts

When Not to Rebalance

If your target allocation itself no longer fits — you are five years from retirement holding a portfolio built for a thirty-year horizon — the answer is to change the target, not to rebalance back to an outdated one. Rebalancing enforces a plan; it does not evaluate whether the plan is still right.

Equally, do not rebalance in response to predictions. Moving to bonds because you expect a recession is not rebalancing, it is market timing wearing a respectable name. The entire value of the discipline comes from following the rule regardless of your opinion about what happens next.

General educational information. Tax consequences depend on your accounts and jurisdiction — consider professional advice before selling appreciated assets.

Sources and further reading

The explanations above are checked against official regulators, statistical agencies, standards bodies and non-profit financial education organisations. Use these primary sources to verify figures and rules before you act on them.

Rebalancing Your Portfolio: When, How Often, and Why It Matters