How to Rebalance a Portfolio: Calendar, Thresholds and Tax-Smart Moves
Markets move, and over time they push a portfolio away from the mix of stocks, bonds and cash it was built around. Rebalancing brings it back. This guide explains why investors rebalance, the main methods, how often people do it, and how to limit taxes and trading costs along the way.
Every portfolio starts with a plan: so much in stocks, so much in bonds, perhaps some cash. Then markets move. After a strong run for stocks, a portfolio that began at 60% stocks and 40% bonds can end up much heavier in stocks than intended, and therefore riskier than the investor signed up for. Rebalancing is the routine of bringing the mix back to its target. It is simple in concept, but the method, the timing and the tax treatment all matter.
What rebalancing does
Rebalancing means selling some of what has grown beyond its target share and buying what has fallen below it, or steering new money toward the underweight part. The goal is risk control, not higher returns. A portfolio's asset allocation is the main driver of how much it can swing in value, so letting it drift means accepting a different level of risk without deciding to.
A simple illustration: suppose a portfolio is set at 60% stocks and 40% bonds. If stocks rise sharply while bonds stay flat, stocks might grow to 70% of the total. If stocks then fall, the portfolio drops further than the original 60/40 plan would have. Rebalancing back to 60/40 locks in some of the gain and resets the risk level.
The flip side is that rebalancing means trimming what has done well and adding to what has lagged. That can feel uncomfortable, and in a long, steady bull market it can mean holding less of the winning asset than a drifting portfolio would. That is the trade-off: lower and more predictable risk in exchange for giving up some upside in certain scenarios.
If you are still setting the target mix itself, our guide to asset allocation and diversification covers how investors think about it.
The main rebalancing methods
| Method | How it works | Strengths | Weaknesses |
|---|---|---|---|
| Calendar | Rebalance on a fixed schedule, such as once a year | Simple, easy to remember, limits trading | Ignores large moves between dates |
| Threshold (bands) | Rebalance when an asset drifts beyond a set band, such as 5 percentage points | Responds to big market moves, avoids pointless small trades | Requires regular monitoring |
| Calendar plus threshold | Check on a schedule, act only if outside the band | Combines discipline with fewer trades | Slightly more rules to follow |
| Cash-flow rebalancing | Direct new contributions or withdrawals toward the underweight asset | Few or no sales, so fewer taxes and costs | Works slowly if cash flows are small relative to the portfolio |
Bands can be set in absolute terms (a 60% stock target with a 5-point band means acting below 55% or above 65%) or in relative terms (a 20% relative band on a 10% holding means acting below 8% or above 12%). Relative bands are useful for small slices of a portfolio, where an absolute 5-point band would be very wide.
How often is enough?
Research from fund companies and academics broadly suggests there is no magic frequency, and the differences between reasonable approaches are usually modest. What matters more is having a rule and following it. A few general patterns:
- Very frequent rebalancing (monthly or more) tends to increase trading costs and, in taxable accounts, realized gains, without a clear improvement in outcomes.
- Annual or semiannual checks are common because they balance discipline with low effort.
- Threshold-based rebalancing means the portfolio is left alone in calm markets and adjusted after large moves, when drift actually matters.
Avoid letting the market's latest headlines decide when to rebalance. The point is to follow a predetermined rule, not to time the market.
Rebalancing with taxes in mind
In the US, where you hold each investment changes what rebalancing costs.
Tax-advantaged accounts first. Selling and buying inside a traditional or Roth IRA, a 401(k), a 403(b) or a similar account generally does not create a tax bill at the time of the trade. If your overall allocation spans several accounts, you can often make most of the adjustment inside these accounts.
Use new money. Direct new 401(k) contributions, IRA contributions or deposits into a brokerage account toward the underweight asset class. Reinvested dividends and interest can be pointed the same way instead of being reinvested automatically into the same fund.
Be careful with taxable sales. Selling an investment held for one year or less at a gain is taxed as a short-term capital gain at ordinary income rates; holding longer than a year usually qualifies for lower long-term rates. The IRS explains the current rules in its guidance on capital gains and losses at irs.gov.
Pair with tax-loss harvesting. If some holdings in a taxable account are below what you paid, selling them can offset gains realized elsewhere. The wash-sale rule limits buying back a substantially identical security within 30 days before or after the sale. Our guide to tax-loss harvesting and the wash-sale rule walks through the details.
Withdrawals count too. Retirees drawing income can take withdrawals from whichever asset class is overweight, which rebalances without separate trades.
A step-by-step rebalancing routine
- List every account. Include 401(k)s, IRAs, HSAs invested in funds, brokerage accounts and any cash you consider part of the plan.
- Total each asset class. Add up US stocks, international stocks, bonds and cash across all accounts, then calculate each as a percentage of the whole.
- Compare with the target. Note which classes sit outside your chosen band.
- Decide the tools. Start with new contributions and tax-advantaged accounts; use taxable sales last.
- Check costs. Most large brokerages charge no commission on stock and ETF trades, but some mutual funds have short-term redemption fees, and spreads still matter for thinly traded funds.
- Place the trades and record them. Keep a simple log of the date, the before-and-after allocation and why you acted.
Automatic and built-in options
Not everyone needs to rebalance by hand.
- Target-date and balanced funds rebalance internally, so the fund manager handles drift.
- Many 401(k) plans offer an automatic rebalancing feature on a quarterly or annual schedule. Check your plan's website or summary plan description.
- Robo-advisors typically rebalance automatically, and some combine it with tax-loss harvesting in taxable accounts.
These tools work best when they cover most of the portfolio. Holding a target-date fund alongside several other funds can produce an overall mix very different from what the target-date fund alone would suggest.
When the target itself should change
Rebalancing restores an existing plan; it does not decide whether the plan still fits. Major life changes, such as approaching retirement, a new job, an inheritance or a change in how much risk you can tolerate, may justify changing the target allocation. Make that decision separately and deliberately, then rebalance to the new target.
The core idea is simple: pick a target, choose a rule for when to act, use tax-advantaged accounts and new cash wherever possible, and keep a record. A modest, repeatable routine does most of the work.
Frequently asked questions
How often should a portfolio be rebalanced?
There is no single correct schedule. Many investors check once or twice a year, or rebalance only when an asset class drifts a set amount from its target, such as five percentage points. Very frequent rebalancing tends to add costs and taxes without clear benefit, while never rebalancing lets risk drift.
Do I pay taxes when I rebalance?
Selling investments at a gain in a regular taxable brokerage account can trigger capital gains tax. Trades inside tax-advantaged accounts such as a 401(k) or IRA generally do not create a tax bill at the time of the trade. Many investors rebalance inside those accounts first, or redirect new contributions, to limit taxable sales.
Do target-date funds rebalance automatically?
Yes. A target-date fund manages its own mix of stocks and bonds and rebalances internally, gradually shifting toward bonds as the target year approaches. If it is your only holding, you generally do not need to rebalance it yourself, though holding it alongside other funds can blur your overall allocation.
