Portfolio Drift & Rebalancing: the ‘maintenance’ that keeps your investments aligned
When people think about investing, they often focus on what they invest in - funds, shares, bonds, property, and so on. But one of the most important (and most overlooked) parts of successful long‑term investing is what happens after you’ve started - keeping your portfolio aligned with your goals and your attitude to risk.
A key concept here is something called ‘portfolio drift’, and the practical solution is rebalancing.
What is portfolio drift?
Most investors begin with a target asset allocation, for example, a mix of shares (equities) and bonds designed to match a goal and a risk level. But markets don’t rise and fall evenly. Over time, one part of your portfolio may outperform another, which causes your actual mix to move away from your target. That’s drift.
What is rebalancing?
Rebalancing is the process of bringing your portfolio back in line with the target allocation - usually by trimming what has grown too large and topping up what has become too small.
It is not about predicting markets. The point of rebalancing is to keep your portfolio aligned to the plan you set for your circumstances.
Why rebalancing matters
It can help to maintain the risk level you signed up for.
If higher‑risk assets grow as a percentage of your portfolio, your overall risk increases—sometimes without you noticing.
It keeps diversification working properly.
A diversified portfolio relies on different assets playing different roles. Drift can quietly undermine that balance.
It means that you stay aligned to your real-world goals.
As your timeline shortens (e.g., approaching retirement, school fees, a house move), the asset mix that suited you years ago may not be appropriate today.
At GDA, this links directly to our advice process: we only provide advice after a detailed appraisal of your current and future circumstances, and we keep plans under review as life evolves.
How often should you rebalance?
There isn’t a single perfect method - what matters is having a consistent process that fits your situation. Two common approaches are:
Calendar rebalancing (e.g., once a year) — straightforward and easy to schedule.
Threshold/band rebalancing (e.g., rebalance if an asset class moves more than a set percentage away from target).
In practice, rebalancing is usually a blend of both approaches.
The Tax Wrapper (a technical detail that really matters)
Rebalancing isn’t just an investment decision, it can also be a tax decision, depending on where your money is held. For example, transactions inside tax-wrapped accounts (such as ISAs or pensions) may be simpler than selling in taxable accounts (where you may need to consider capital gains implications). Either way, it’s important that rebalancing is done thoughtfully and in the context of your wider financial picture.
This is one reason an adviser will look at your overall position - income, expenditure, goals, and attitude to risk, before recommending or adjusting an investment strategy.
How we approach this at GDA
Our role is to help clients build an investment strategy that reflects their circumstances and objectives, then keep it on track over time - reviewing performance, revisiting risk attitude, and making appropriate adjustments when needed. Our advisers always keep up-to-date with the markets, funds and fund management strategies, to ensure that our advice remains suitable for our client base.
As independent advisers, we aim to provide impartial advice tailored to individual needs—so the right approach to rebalancing will depend on your time horizon, goals, and comfort with volatility.
In Summary
Drift happens naturally as markets move.
Rebalancing is a disciplined way to keep your portfolio aligned with the risk level and objectives you set.
The best approach is the one that is consistent, understandable, and suitable for your circumstances - and reviewed as life changes.
This article is for general information only and does not constitute financial advice. Investment values can go down as well as up, and past performance is not a reliable indicator of future results. If you’re unsure what’s best for you, seek independent financial advice.