There’s an investing concept that gets discussed often but explained badly. The financial industry treats it as a sophisticated technique requiring careful judgment and ideally professional help. The honest truth is that rebalancing your portfolio is one of the simpler maintenance jobs in long-term investing, and most ordinary investors either don’t need to do it at all (their fund handles it for them) or need to do it about once a year for ten minutes.
This post is the no-nonsense version: what rebalancing actually means, why it matters, when to do it, and the situations where you can ignore the whole topic entirely.
What rebalancing actually means
Imagine you decide that your ideal long-term portfolio is 80% global equities and 20% bonds. You set this up in your ISA, with the right proportions on day one.
A year later, equities have done well and bonds have done less well. Your portfolio is now 87% equities and 13% bonds. The equities have grown faster, so they now account for a bigger slice of the pie.
Two years later, equities have continued to outpace bonds, and you’re at 91% equities and 9% bonds. The original 80/20 ratio you started with has drifted significantly.
Rebalancing means adjusting your holdings back to your target ratio. You sell some equities and buy some bonds (or, more practically, direct your new contributions disproportionately toward bonds) until the split is back to 80/20.
That’s the whole concept. It’s a maintenance task that prevents your portfolio’s risk profile from drifting away from what you originally chose.
Why people do it
Two main reasons.
1. Risk management. When equities have a great run, your portfolio becomes more equity-heavy than you intended. That means it’ll fall harder if equities crash. Rebalancing back to your target ratio keeps the risk in line with what you decided was appropriate for your situation.
2. The “buy low, sell high” effect. When you sell whatever has done best and buy whatever has done worst, you’re mechanically following the textbook investing rule. You’re not predicting anything; you’re just resetting back to your target. Over decades, this disciplined behaviour can produce a small return advantage, though the size of the effect is debated.
The first reason is the more important one. The “buy low, sell high” benefit is real but modest, and isn’t worth obsessing over. Risk management is the main job rebalancing actually does.
When to rebalance
There are two common approaches.
Calendar-based. Pick a date each year (your birthday, the start of the new tax year, January 1st) and rebalance then, regardless of what the market has done. The advantage is simplicity. The disadvantage is that you might rebalance unnecessarily in years when nothing has drifted very much.
Threshold-based. Set a rule like “rebalance if any asset class drifts more than 5 percentage points from target.” Wait until your portfolio actually needs it, then act. The advantage is that you only rebalance when it matters. The disadvantage is that you have to check periodically to know whether you’ve hit the threshold.
The honest answer is that for most ordinary investors, calendar-based rebalancing once a year is plenty. The marginal benefit of more frequent rebalancing is small, and frequent rebalancing actually increases costs (trading fees, bid-ask spreads, time spent thinking about it).
A simple annual review, ideally tied to something you already do (a tax year roll-over, a year-end financial review, your annual ISA top-up), is enough.
Why all-in-one funds make this disappear
Here’s the part most articles on rebalancing skip: many UK investors don’t need to rebalance at all, because their fund does it for them.
If you hold a multi-asset fund (Vanguard LifeStrategy, HSBC Global Strategy, Royal London GMAP), the fund itself rebalances internally. The fund manager keeps the equity and bond proportions at the stated target (60/40, 80/20, or whatever the variant is) by trading within the fund. You never need to do anything; your single holding always reflects the stated risk profile.
The same is true for target-date funds, which automatically shift toward more conservative allocations as you approach retirement.
For investors using these all-in-one structures, “rebalancing” is a topic that can be safely ignored. You bought a fund that does the maintenance for you. The fee for this is typically modest (multi-asset funds usually charge 0.20% to 0.40% per year, against 0.13% to 0.23% for a pure equity tracker), and for most ordinary investors it’s well worth the simplicity.
A great deal of “rebalancing advice” online is solving a problem that the fund industry already solved by providing all-in-one products. Simple Investing for Absolute Beginners covers how to choose between an all-in-one fund and a do-it-yourself approach, and which suits which kind of investor.
When rebalancing genuinely matters
A few situations where rebalancing is worth thinking about properly:
You hold multiple individual funds. If your portfolio is, say, a global equity tracker plus a UK gilt fund plus an emerging markets fund, the proportions will drift over time. Without rebalancing, your asset allocation drifts wherever the market takes it.
You’re approaching retirement. As your time horizon shortens, you typically want to shift toward more bonds and less equity. Rebalancing during this transition is more important than during the accumulation phase.
Your time horizon or circumstances have changed. If you originally chose 80/20 because you had a 30-year horizon, and you now have a 10-year horizon, your target ratio probably needs adjusting. This is less “rebalancing” and more “redesigning,” but it has the same mechanics.
A market move has been very large. After a 2008 or 2020-style crash, some investors find their portfolio is dramatically overweight bonds (because equities fell hard). Rebalancing in these situations means selling bonds and buying equities, which historically has been a profitable move, even though it feels uncomfortable at the time.
The contributions trick
For investors still in the accumulation phase, there’s a useful technique that makes rebalancing largely automatic without needing to sell anything.
Instead of selling overweight assets and buying underweight ones, direct your new monthly contributions disproportionately toward whichever asset class has fallen below target. If your equities have grown to 85% (above your 80% target), point your next few months of contributions entirely at bonds. The new money pushes the proportions back toward target without triggering any sales.
This is a cleaner approach than active rebalancing for several reasons:
- No selling means no capital gains tax events outside ISAs and pensions.
- No trading fees.
- It feels less like “tinkering” and more like a natural extension of your contribution plan.
For someone contributing £500 a month to a £100,000 portfolio, the contribution-direction approach can keep the portfolio close to target without ever needing to do a “real” rebalancing transaction. We covered the contribution discipline angle in our post on the 10-year test, which is worth reading alongside this one.
The tax angle
If your portfolio is entirely inside ISAs and SIPPs, rebalancing is tax-free. You can sell whatever you want, in any quantity, without owing HMRC anything. Rebalance freely.
If you have significant holdings in a general investment account (GIA), rebalancing is more complicated. Selling investments at a profit triggers capital gains tax above the £3,000 annual exempt amount. Frequent rebalancing in a GIA can quickly create real tax bills.
For GIA holdings, the contribution-direction approach is doubly useful, because it lets you reshape the portfolio without triggering CGT events. Where active rebalancing is needed, the standard approach is to do it gradually, keeping each year’s gains under the annual exempt amount.
How most people overcomplicate it
A few common mistakes that turn rebalancing into a problem:
Rebalancing too often. Monthly or quarterly rebalancing rarely improves outcomes and often costs money. Annually is plenty for most portfolios.
Rebalancing to overly precise targets. “I’m at 79.5% equities, my target is 80%.” This is not a reason to rebalance. Markets will drift the figures around continually. Setting a meaningful threshold (5 percentage points or so) prevents constant fiddling.
Treating rebalancing as a return-enhancing strategy. It isn’t, mainly. It’s a risk-management technique. The “buy low, sell high” benefit is real but small, and shouldn’t be the primary motivation.
Rebalancing toward whatever’s in fashion. Some investors look at their portfolio, notice that emerging markets are doing well, and decide to “rebalance” by adding more emerging markets. That’s not rebalancing. That’s chasing returns under a different name.
Failing to rebalance at all. The opposite mistake. After 10 years without any maintenance, an “80/20” portfolio may have drifted to 95/5 without anyone noticing. The risk profile is now completely different from what was intended.
A simple annual checklist
For investors holding individual funds rather than all-in-one structures, here’s a sensible annual rebalancing routine:
- Look at your current asset allocation. What percentage in equities, bonds, cash, anything else?
- Compare to your target. Has anything drifted by more than 5 percentage points?
- If yes, decide whether to rebalance by selling-and-buying, or by directing your next 6 months of contributions toward the underweight asset class.
- If no, do nothing. You’re fine.
- Check that your target itself still makes sense given your time horizon and circumstances. If they’ve changed, update the target.
- Do this once a year. Set a calendar reminder. Don’t think about it the rest of the time.
The whole exercise should take 15 minutes or less in most years.
| Want a clearer guide to managing a UK investment portfolio without overcomplicating it? Simple Investing for Absolute Beginners covers fund selection, asset allocation, and the simple long-term maintenance habits that actually matter. [ Find out more → ] |
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Rebalancing is one of those investing concepts that financial industry marketing has made to sound far more complex than it actually is. The honest reality is that for most UK investors, rebalancing is either handled automatically by an all-in-one fund, or done in a quiet 15-minute annual session that involves no drama and very little decision-making. Worth doing properly, but never worth obsessing over.
This article is for information and education only and does not constitute financial advice. Investments can fall as well as rise in value and you may get back less than you invest. Past performance is not a reliable indicator of future results.