By Christian BrinkleyLicensed NC Insurance Agent, NPN 22217190, NC Life & Health · Updated October 14, 2026 · 4 min read
Your Portfolio Drifts Without You
You set up your investments with a plan: 80 percent stocks, 20 percent bonds. Sensible for your age. Then you do not touch it for three years.
Stocks have a great run. Bonds plod along. You check your account and find you now hold 90 percent stocks and 10 percent bonds. You did not choose that. The market chose it for you.
Why It Matters
The main reason is risk control. An 80/20 portfolio behaves very differently from a 90/10 portfolio. The drifted version is riskier than what you signed up for. If stocks then crash, you lose more than your plan allowed for.
Rebalancing puts a ceiling on that drift. It keeps your portfolio's risk level roughly where you decided it should be, instead of letting good years quietly turn you into a more aggressive investor than you intended.
When to Rebalance
There are two main approaches, and both work.
Calendar rebalancing means you rebalance on a schedule: once a year, twice a year, whatever you pick. Annual rebalancing is the most common recommendation. It is simple, it is easy to remember, and it keeps trading to a minimum.
Threshold rebalancing, sometimes called band rebalancing, means you rebalance whenever an asset drifts too far from its target. A common band is 5 percentage points. If your stock target is 80 percent and stocks drift above 85 or below 75, you rebalance. Otherwise you leave it alone.
Three Simple Methods
Method one: sell and buy. This is the direct approach. Sell enough of the overweight asset and use the proceeds to buy the underweight one until you hit your targets. In a 401(k) or IRA, this costs nothing in taxes. In a taxable account, selling can trigger capital gains taxes, so this method is best inside retirement accounts.
Method two: redirect new contributions. Instead of selling anything, point your new deposits at the lagging asset. If stocks are overweight, send your next few months of 401(k) contributions entirely to bonds until the mix is back in line.
A Hypothetical Example
Say you start the year with 8,000 dollars in a stock fund and 2,000 in a bond fund. That is your 80/20 target on a 10,000 dollar portfolio.
Stocks have a great year and grow 25 percent. Bonds grow 5 percent. Now you have 10,000 in stocks and 2,100 in bonds, for a total of 12,100. Stocks are now about 83 percent of the portfolio. Close to target, but drifting.
Rebalancing and Taxes
Inside retirement accounts like 401(k)s and IRAs, rebalancing is tax free. Sell and buy as much as you want. No tax forms, no consequences.
In a taxable brokerage account, selling an investment that gained value triggers capital gains tax. That does not mean you should never rebalance a taxable account. It means you should be thoughtful about it.
Common Mistakes
The biggest mistake is never rebalancing at all. Set a calendar reminder. Annual is fine.
The second is rebalancing too often. Checking every week and trading on every wiggle racks up costs and taxes for no benefit. Once or twice a year is plenty.
The third is rebalancing into a panic. Rebalancing is a calm, scheduled activity. If the market is crashing and you feel sick, that is not the moment to redesign your targets. Stick to the plan you made when you were thinking clearly, or wait until you are thinking clearly again.
The Bottom Line
Rebalancing is maintenance, not excitement. Pick a target mix, check it once a year, and nudge it back in line with new contributions or a simple sell and buy. Inside retirement accounts it is easy and tax free.
This is general educational information, not financial advice. Portfolio decisions depend on your full situation, so talk to a qualified professional before making big moves.
Questions people ask me about this
Why do it matter?
The main reason is risk control. An 80/20 portfolio behaves very differently from a 90/10 portfolio. The drifted version is riskier than what you signed up for. If stocks then crash, you lose more than your plan allowed for. Rebalancing puts a ceiling on that drift.
When to rebalance?
There are two main approaches, and both work. Calendar rebalancing means you rebalance on a schedule: once a year, twice a year, whatever you pick. Annual rebalancing is the most common recommendation. It is simple, it is easy to remember, and it keeps trading to a minimum.
What should I know about rebalancing portfolio?
You set up your investments with a plan: 80 percent stocks, 20 percent bonds. Sensible for your age. Then you do not touch it for three years. Stocks have a great run. Bonds plod along. You check your account and find you now hold 90 percent stocks and 10 percent bonds. You did not choose that. The market chose it for you.
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