ETF Rebalancing — When and How
Rebalancing means periodically restoring your portfolio to its target allocation (for example, back to 70/30) after market moves have shifted the weights. It keeps your risk level in check and automatically enforces “buy low, sell high”. Most investors do it once a year — or whenever a position drifts more than roughly 5 percentage points away from its target.
Why rebalance at all?
Over time the asset classes in your portfolio drift apart: when stocks rise sharply, their weight grows — and with it your risk — beyond the level you planned. A deliberate 70/30 portfolio (70 % equities, 30 % bonds/cash) quietly turns into a riskier 80/20. Rebalancing restores the original mix and does two things for you:
- Risk control: your portfolio stays as risky as you originally intended — not as risky as the last bull market happened to make it.
- Discipline over gut feeling: you automatically sell what has become expensive and buy more of what is cheap — “buy low, sell high” as a rule, not a hope.
- No market timing: rebalancing is a mechanical rule that stops you chasing returns pro-cyclically.
The two methods for rebalancing
There are two ways back to your target allocation. The first is almost always the better one because it triggers no tax:
- (a) Redirect new money (preferred, tax-free): you steer your regular contributions and any new cash into the underweight asset class until the target weighting is restored. Nothing is sold, so no capital-gains tax is triggered. Ideal during the accumulation phase.
- (b) Sell to rebalance: you sell part of the overweight position and use the proceeds to top up the underweight one. This works instantly and precisely — but realising price gains may trigger capital-gains tax.
Threshold or calendar? When to rebalance
On the “when”, two approaches have become standard — and many investors combine them:
- Calendar-based: you check and correct on a fixed date, classically once a year (e.g. every January). Simple, predictable, low effort.
- Threshold-based (tolerance band): you act only when a position drifts more than ~5 percentage points from target (so 70 % becomes >75 % or <65 %). It reacts to the market rather than the calendar.
- Combination: review once a year, but only trade if the 5 pp band has been breached — a good compromise between effort and precision.
Example: rebalancing a 70/30 portfolio (€100,000)
| Asset class | Target | After market move | After rebalancing |
|---|---|---|---|
| Equity ETF | 70 % (€70,000) | 78 % (€85,800) | 70 % (€77,000) |
| Bonds / cash | 30 % (€30,000) | 22 % (€24,200) | 30 % (€33,000) |
| Drift from target | 0 pp | +8 pp → band breached | 0 pp → back on target |
In the example, the equity weight reached 78 % after a rally — 8 percentage points above target. To stay tax-free, you direct your next contributions entirely into the safe sleeve. To correct instantly and exactly, you sell €8,800 of the equity ETF and move it into cash — which may incur capital-gains tax on the gain portion.
🌍 The tax angle when you sell
Whenever you sell a holding that has gained in value to rebalance, you realise that gain — and a realised gain is generally taxable. The exact rules vary by country, so check your local rules. As a concrete example, in Germany a realised gain is subject to a flat 25 % capital-gains tax (Abgeltungsteuer) plus solidarity surcharge; for equity ETFs a 30 % partial exemption (Teilfreistellung) means only 70 % of the gain is taxed, and the first €1,000 of gains per year is tax-free via the saver’s allowance. Key takeaways that apply broadly:
- Selling to rebalance can trigger tax on the realised gain, whereas redirecting new money sells nothing and so triggers no tax.
- Use tax-free allowances first: many countries have an annual capital-gains allowance — small rebalancing sales below it cost no tax.
- Rules, rates and allowances differ between Germany, Spain, Italy and elsewhere — always confirm the treatment in your own country before selling.
Frequent rebalancing feels diligent but eats returns: every sale can trigger capital-gains tax on realised gains, plus order fees and spreads. Studies show that annual or threshold-based rebalancing delivers almost the same risk benefit as monthly rebalancing — at a fraction of the cost. Rebalance rarely but consistently, and prefer the tax-free method of redirecting new contributions. This is not tax advice; rules vary by country, so confirm your specific situation with a local tax adviser.
FAQ — ETF rebalancing 2026
What does rebalancing an ETF portfolio mean?
Rebalancing means periodically restoring your portfolio to its original target allocation after market moves have shifted the weights. Example: a 70/30 portfolio (70 % equities, 30 % bonds) might drift to 78/22 after an equity rally. Rebalancing brings it back to 70/30 — either by directing new contributions into the underweight part or by selling part of the overweight part. This keeps your risk at the planned level and automatically buys more of whatever has fallen.
How often should I rebalance?
For most investors, once a year (calendar-based) or whenever a position drifts more than about 5 percentage points from its target (threshold-based) is enough. Both deliver almost the same risk benefit as rebalancing more often, but with far lower costs and taxes. Frequent rebalancing usually isn’t worth it.
Does rebalancing trigger capital-gains tax?
Only if you sell holdings that have gained in value — that realises the gain, which is generally taxable. Rates and allowances vary by country: as an example, Germany applies a flat 25 % tax plus solidarity surcharge, with a 30 % partial exemption for equity ETFs and a €1,000 annual tax-free allowance. If instead you simply redirect new contributions into the underweight asset class, nothing is sold and no capital-gains tax is triggered. Always check your local rules.
Should I rebalance by selling or with new money?
If you are still contributing regularly, redirecting new money into the underweight asset class is almost always better: it triggers no tax and costs no extra order fees. You only need to sell and reallocate when the drift is too large to fix through new contributions alone — or when you are no longer saving but already drawing down the portfolio.