We’re Great at Buying. Terrible at Everything After.
Every investing guide in the world tells you what to buy. Very few tell you what happens next. When do you sell? How often should you rebalance? What triggers a change? What if one ETF has massively outperformed — do you trim it or let it ride?
These questions haunt investors far more than the initial purchase decision. And the lack of clear answers leads to two opposite but equally harmful behaviors:
The tinkerer — constantly adjusting, selling winners too early, chasing new hot ETFs, and generating tax bills through excessive trading.
The ignorer — never looking at their portfolio, letting allocations drift wildly, and waking up one day to discover they’re 95% in tech when they intended to be diversified.
The sweet spot is somewhere in between. Let me walk you through a practical system that takes about 30 minutes per year.
The Only Legitimate Reasons to Sell an ETF
Before we talk about rebalancing, let’s address the elephant: when should you actually sell an ETF entirely?
There are very few good reasons. Here they are:
1. Your Goal or Time Horizon Changed
You started investing for retirement at 30, and now you’re 55. Your risk tolerance is different. Shifting from 90% stocks to 70% stocks makes sense. This might mean selling some stock ETF shares and buying bond ETFs.
Or maybe you were saving for a house down payment and you’ve reached your target. Selling to use the money for its intended purpose is completely rational.
2. The ETF Changed Fundamentally
The ETF’s index methodology changed in a way that no longer matches your goals. The expense ratio increased significantly. The fund is being closed or merged. The tracking error became unacceptable. These are structural reasons that justify switching to a comparable alternative.
3. You Found a Materially Better Alternative
You own SPY at 0.0945% and discover VOO at 0.03%. Same index, same exposure, one-third the cost. In a tax-advantaged account (IRA, 401k), this switch is a no-brainer — there are no tax consequences. In a taxable account, you need to weigh the tax cost of selling against the ongoing fee savings.
4. Tax-Loss Harvesting
Your ETF is down, and you can sell it at a loss to offset gains elsewhere in your portfolio. You immediately buy a similar (but not “substantially identical”) ETF to maintain your market exposure while locking in the tax benefit. This is a legitimate tax strategy that we’ll cover more below.
That’s It. That’s the List.
Notice what’s NOT on the list:
- ❌ “The market is going down” — You don’t know that, and selling to cash is market timing.
- ❌ “This ETF hasn’t done well lately” — Short-term underperformance isn’t a reason to sell a fundamentally sound investment.
- ❌ “I heard a recession is coming” — Everyone always thinks a recession is coming. Acting on predictions is not a strategy.
- ❌ “I want to lock in my gains” — Selling winners to “lock in gains” just triggers taxes and removes your money from a compound growth vehicle.
- ❌ “My friend told me about a better ETF” — Maybe it is better. But the tax cost and disruption of switching might not be worth it.
How Portfolio Drift Happens
You start with a clean allocation: 60% VTI, 25% VXUS, 15% BND. After a year, the US market rose 15%, international was flat, and bonds returned 3%.
Your portfolio is no longer 60/25/15. It’s something like:
| ETF | Target | Current (after drift) |
|---|---|---|
| VTI | 60% | 65% |
| VXUS | 25% | 22% |
| BND | 15% | 13% |
Your US stock allocation crept up because it outperformed. Your international and bond allocations shrank in relative terms. If this continues for several years without correction, you could end up at 75% US / 15% International / 10% bonds — significantly more aggressive and less diversified than you intended.
This is portfolio drift, and it happens silently. It’s not a crisis, but left unchecked, it changes your risk profile in ways you didn’t choose.
The Simple Rebalancing System
Here’s the system I recommend. It’s based on time intervals plus threshold triggers:
Check Once Per Year
Pick a date — your birthday, January 1st, tax day, whatever is easy to remember. On that date, log into your brokerage and compare your current allocation to your target.
The 5% Rule
If any asset class has drifted more than 5 percentage points from its target, rebalance.
| ETF | Target | Current | Drift | Action? |
|---|---|---|---|---|
| VTI | 60% | 63% | +3% | No (under 5%) |
| VXUS | 25% | 23% | -2% | No |
| BND | 15% | 14% | -1% | No |
In this case, you’d do nothing. The drift is within tolerance.
| ETF | Target | Current | Drift | Action? |
|---|---|---|---|---|
| VTI | 60% | 68% | +8% | Yes (over 5%) |
| VXUS | 25% | 20% | -5% | Yes (at 5%) |
| BND | 15% | 12% | -3% | Consider |
Here, VTI has drifted 8 points above target and VXUS is 5 points below. Time to rebalance.
How to Rebalance
You have two methods:
Method 1: Redirect new contributions (preferred)
Instead of selling anything, direct your monthly contributions entirely toward the underweight positions until the allocation corrects. If VXUS is underweight, put your next several months of investment money into VXUS instead of splitting across all three.
This is the tax-friendliest approach. No selling means no capital gains taxes. It’s slower, but for younger investors with regular contributions, it works well.
Method 2: Sell and redistribute
Sell enough of the overweight position and buy the underweight positions to restore your target allocation.
In a tax-advantaged account (IRA, 401k), there are zero tax consequences. Just sell and buy freely.
In a taxable account, selling triggers capital gains taxes. You’ll owe taxes on any profits from the sold shares. This might still be worth doing if the drift is large (10%+ from target), but for small adjustments, Method 1 is usually smarter.
The Rebalancing Bonus: Forced Discipline
Here’s what’s counterintuitive about rebalancing: it forces you to sell your winners and buy your losers. That feels wrong. Why would you sell the thing that’s doing well and buy the thing that’s not?
Because markets are cyclical. The asset that outperformed this year often underperforms in subsequent years, and vice versa. Rebalancing captures some of those gains and redeploys them into assets likely to catch up.
Studies have shown that disciplined annual rebalancing can add 0.3-0.5% per year to returns compared to a never-rebalanced portfolio — not because each rebalancing event is profitable, but because it systematically enforces a buy-low, sell-high discipline over many cycles.
More importantly, rebalancing keeps your risk profile stable. Without it, a portfolio naturally becomes more aggressive over time (because stocks tend to outperform bonds, their weight grows). If you originally chose 60/40 because that’s what let you sleep at night, you need to maintain that ratio — not let it drift to 80/20 during a bull market and then panic when the inevitable correction hits harder than expected.
Tax-Loss Harvesting: The Advanced Move
Tax-loss harvesting (TLH) is one of the few legitimate “free lunch” opportunities in investing. Here’s how it works:
The Concept
When an ETF in your taxable account is trading below what you paid for it, you can sell it to realize a capital loss. That loss offsets capital gains elsewhere in your portfolio, reducing your tax bill.
After selling, you immediately buy a similar (but not “substantially identical”) ETF to maintain your market exposure.
A Practical Example
You bought VTI at $280/share. It’s now at $250/share. You have $30/share in unrealized losses.
- Sell VTI — Realize the $30/share loss
- Immediately buy ITOT (iShares Total Market ETF) — Same exposure, different fund
- Claim the loss on your taxes — It offsets capital gains, saving you real money
The result: your portfolio hasn’t changed in any meaningful way (ITOT and VTI hold essentially the same stocks), but you’ve generated a tax deduction.
The Wash Sale Rule
The IRS has a rule: you can’t sell an investment at a loss and buy a “substantially identical” investment within 30 days before or after the sale. If you do, the loss is disallowed.
This is why you swap to a different ETF that tracks a similar (but not identical) index:
| Sell | Buy Instead |
|---|---|
| VTI (CRSP Total Market) | ITOT (S&P Total Market) |
| VOO (S&P 500) | IVV (S&P 500 — debatable, see below*) |
| VXUS (FTSE Intl) | IXUS (MSCI Intl) |
| BND (Bloomberg Bond) | AGG (Bloomberg Bond — debatable*) |
*Note: Whether swapping between ETFs that track the same index (like VOO and IVV) violates the wash sale rule is a gray area. The IRS hasn’t provided definitive guidance. Many tax professionals consider it acceptable since they’re different securities from different issuers, but consult a tax advisor for your specific situation.
When It Makes Sense
TLH is most valuable when:
- You have significant capital gains to offset (from selling other investments or from realized gains distributions)
- You’re in a high tax bracket
- The loss is large enough to justify the effort
For small accounts or minor losses, the hassle may not be worth it. But for larger portfolios in taxable accounts, TLH can save thousands in taxes over an investing lifetime.
How Often Is Too Often?
| Frequency | Verdict |
|---|---|
| Daily/Weekly | Way too much. Generates taxes and trading costs with no benefit. |
| Monthly | Still too much for most people. Only if you have a very specific, rules-based system. |
| Quarterly | Borderline. Okay if you check but only act when drift exceeds thresholds. |
| Annually | Ideal for most investors. Provides structure without over-activity. |
| Never | Too little. Multi-year drift can significantly change your risk profile. |
Research from Vanguard suggests that annual rebalancing using tolerance bands (the 5% rule) captures most of the benefit with minimal cost and effort. More frequent rebalancing doesn’t meaningfully improve outcomes and can increase tax drag.
Real-World Rebalancing: Step by Step
Let’s walk through a concrete annual rebalance.
Portfolio: $100,000 across VTI (60%), VXUS (25%), BND (15%) Account type: Roth IRA (no tax concerns) Date: Your annual review
Step 1: Check current values
| ETF | Shares | Current Price | Current Value | Current % | Target % |
|---|---|---|---|---|---|
| VTI | 215 | $295 | $63,425 | 63.4% | 60% |
| VXUS | 390 | $62 | $24,180 | 24.2% | 25% |
| BND | 168 | $74 | $12,432 | 12.4% | 15% |
| Total | $100,037 | 100% | 100% |
Step 2: Calculate target values
| ETF | Target % | Target Value | Difference |
|---|---|---|---|
| VTI | 60% | $60,022 | -$3,403 (sell) |
| VXUS | 25% | $25,009 | +$829 (buy) |
| BND | 15% | $15,006 | +$2,574 (buy) |
Step 3: Execute trades
- Sell $3,403 of VTI (~11.5 shares)
- Buy $829 of VXUS (~13.4 shares)
- Buy $2,574 of BND (~34.8 shares)
Step 4: Verify and move on
Confirm your allocation is back to 60/25/15. Set a calendar reminder for next year. Close your brokerage app. Go enjoy your life.
Total time: about 15-20 minutes. That’s your entire portfolio maintenance for the year.
The Rebalancing Mindset
Rebalancing isn’t exciting. It’s not supposed to be. It’s the financial equivalent of changing your car’s oil — a brief, boring maintenance task that prevents much bigger problems down the road.
The investors who build the most wealth aren’t the ones making brilliant tactical moves. They’re the ones who set a reasonable plan, follow it mechanically year after year, and don’t let emotions or market noise push them off course.
Set your allocation. Rebalance annually. Trust the process.
Need to check if your portfolio needs rebalancing? Our free ETF Portfolio Analyzer shows your current allocation and highlights any positions that may have drifted from your targets.