Rebalancing your portfolio

Suppose you start with an 80/20 stocks/bonds allocation. Stocks do great for three years and now you're at 90/10. Your portfolio is now riskier than you intended — not because you chose to take more risk, but because the market chose for you. Rebalancing is the act of periodically bringing your allocation back to your target.

Why it matters

• Maintains the risk level you actually chose, instead of drifting with whatever's hot.
• Forces a 'sell high, buy low' discipline — you trim what went up and add to what went down.
• Over decades, a small but real return boost in certain conditions (the rebalancing bonus).

How often to rebalance

Once a year is plenty. More often than that usually just creates trading costs and taxes without improving returns. A popular alternative: rebalance whenever any asset class drifts more than 5 percentage points from its target (so if you want 60% stocks, rebalance when you hit 65% or 55%).

Target-date funds handle this for you

If your entire portfolio is inside a single target-date fund (common in 401ks), rebalancing happens automatically inside the fund. You don't need to do anything. This is one of the reasons target-date funds are a legitimately good default for most people.

A worked example with real numbers

You hold $100,000 at a 60/40 target: $60,000 in a total stock fund, $40,000 in a total bond fund. Over eighteen months, stocks rally 30% and bonds earn 3%. Now you have $78,000 in stocks and $41,200 in bonds — $119,200 total, sitting at roughly 65/35. Rebalancing means selling about $6,500 of stocks and buying bonds to restore 60/40 ($71,500 / $47,700). Notice what just happened: you systematically sold an asset after it rose 30% and bought one that lagged, with zero forecasting involved. Now run the tape forward to a crash: stocks drop 35%, and rebalancing has you buying stocks near the bottom with bond money. Nobody rebalancing on a rule feels good doing it — in booms it feels like leaving the party early, in busts like catching a falling knife. The discipline is precisely the point: it's the only reliable mechanism most investors have for buying low and selling high.

Where to rebalance: account order matters

Selling winners in a taxable brokerage account triggers capital gains tax, which can easily eat the benefit. So rebalance in this order: first, direct new contributions to the underweight asset (no selling, no taxes). Second, do any actual selling inside tax-advantaged accounts — 401(k)s and IRAs — where trades have no tax consequences. Third, in taxable accounts, use dividend payouts (turn off automatic reinvestment and point the cash at the underweight asset) before resorting to sales. Most people with ongoing contributions and a 401(k) can stay balanced for decades without ever generating a taxable event.

1. 1
   Pick your trigger

   Either a calendar date (every January, or your birthday) or a threshold (any asset 5 percentage points off target). Threshold rebalancing responds faster to big moves; calendar rebalancing is easier to remember. Both work. Pick one and write it down.

2. 2
   Check your actual allocation across all accounts

   Add up stocks and bonds across your 401(k), IRAs, and brokerage together. Most brokerages and free tools like Empower show this in one view. Compare against your target.

3. 3
   Rebalance with the tax-smart hierarchy

   New contributions first, then trades inside retirement accounts, then dividends in taxable, then — only if still needed — actual taxable sales, preferring lots held over a year for long-term gains rates.

4. 4
   Ignore it until the next trigger

   Rebalancing more than a couple of times a year adds costs and taxes without adding return. Studies repeatedly find annual rebalancing captures nearly all the benefit. This is a 30-minute-per-year job.

Common rebalancing mistakes

• Skipping it during crashes, when it matters most. Rebalancing into stocks in March 2009 or March 2020 was exactly what the rule prescribed — and exactly when most people abandoned the rule.
• Rebalancing every month. Studies show frequent rebalancing mostly generates transaction costs and taxes. Momentum means winners tend to keep winning for months; annual or 5%-threshold rebalancing captures the benefit without fighting that.
• Treating it as a return-maximizing tool. Rebalancing is primarily risk control. Over some periods, never rebalancing (letting stocks run) earns more — with far more risk than you signed up for. Judge it by whether your risk stayed on target, not whether it beat buy-and-hold.
• Forgetting that rebalancing includes bonds-to-stocks. Everyone remembers to trim stocks after a rally; fewer remember the rule also commands buying stocks after a 30% crash. It's one rule, and it only works if you follow both halves.

Rebalancing with new money: the tax-free method

If you are still contributing regularly, you may rarely need to sell anything at all. Instead of splitting every contribution to match your target percentages, direct each new dollar toward whichever asset is furthest below target. Suppose your target is 70/30 and a strong stock year has pushed you to 76/24: route the next several months of contributions entirely into bonds until the ratio drifts back. In a taxable account this matters doubly, because selling winners to rebalance realizes capital gains, while buying the laggard costs nothing in tax. The same logic applies to dividends — turn off automatic reinvestment in a taxable account and manually direct the cash to whatever is underweight. For most accumulators under 50, contribution steering alone keeps the portfolio within a few points of target for years at a time.

Thresholds versus calendars: picking your trigger

There are two standard triggers, and the differences are smaller than people expect. Calendar rebalancing — once a year, on your birthday or in January — is simple and hard to fumble. Threshold rebalancing — act whenever an asset drifts more than 5 percentage points from target — responds faster to big moves but requires you to actually monitor the portfolio. Vanguard's research found that most reasonable variations produce long-run results within a fraction of a percent of each other. What genuinely hurts is either extreme: rebalancing monthly (transaction costs, taxes, and constantly cutting your winners) or never rebalancing at all, which lets a 60/40 portfolio silently morph into 80/20 over a decade and deliver its surprise during the next crash. Pick either trigger, write it down, and follow it mechanically.

However you trigger it, keep the paperwork trivial: a one-page note listing your target percentages, your rebalancing rule, and which account to trade in is enough to make the whole process a fifteen-minute annual chore instead of a recurring judgment call.