Investment guide
What is asset allocation?
Asset allocation is how an investment portfolio is divided between different types of assets — such as shares, bonds, cash and property. That mix is one of the main ways a portfolio balances potential growth with investment risk.
Building blocks
Different asset classes behave differently.
MoneyHelper identifies four broad mainstream asset classes: shares, cash, property and fixed-interest securities such as government and corporate bonds.
Shares
Ownership in companies. Shares can provide long-term growth and income potential but can fluctuate significantly in value.
Bonds
Loans to governments or companies. They can provide income and may behave differently from shares, but their value can still rise or fall.
Cash
Generally more stable in nominal value, but returns may fail to keep pace with inflation.
Property
Property exposure can provide income and diversification, but values can fall and some property investments can be difficult to sell quickly.
The portfolio mix
Asset allocation determines where the portfolio's risks and opportunities come from.
A portfolio holding mostly shares will usually behave differently from one holding a larger proportion in bonds and cash. Changing the mix therefore changes the types and amount of investment risk being taken.
There is no single asset allocation that is suitable for everyone. Two investors with the same amount of money might need very different portfolios because their objectives, timescales and financial circumstances differ.
Even a well-diversified portfolio can fall in value. The purpose is to construct a mix of risks that is appropriate for the investor and the objective.
Risk & timeframe
The appropriate mix can change depending on when the money is needed.
MoneyHelper says investing is generally more appropriate for longer-term goals, commonly five years or more, because short-term market falls can be particularly damaging when money must be withdrawn at a fixed point.
Someone with decades before needing the money may have greater ability to tolerate market fluctuations than someone approaching a major planned withdrawal. But timeframe is only one consideration: capacity for loss and personal tolerance for investment risk also matter.
Attitude to risk
How comfortable are you with uncertainty and seeing the portfolio move up and down?
Capacity for loss
What would a significant investment loss actually do to your financial plans and standard of living?
Diversification
Asset allocation and diversification work together.
The FCA explains diversification as spreading investments across different products and markets so the portfolio is less dependent on one investment performing well.
Diversification can happen between asset classes and within them. A share allocation, for example, might be spread across many companies, sectors and geographic regions rather than relying on one market.
It can reduce reliance on individual holdings or markets, but a diversified portfolio can still lose money when markets fall.
Keeping the mix aligned
Market movements can change your asset allocation over time.
If shares rise faster than the rest of a portfolio, they can gradually become a larger percentage of it. The portfolio may then be taking more equity risk than originally intended even though no deliberate change was made.
Rebalancing means adjusting holdings to bring the portfolio back towards its intended allocation. This might involve selling assets that have become overweight, adding to underweight areas or directing new contributions differently.
Rebalancing is about maintaining the investment strategy — not trying to predict every short-term market movement.
Putting it into practice
You do not necessarily need to buy each asset individually.
MoneyHelper notes that pooled investment funds can hold a range of assets and can make diversification easier. Some funds focus on a single asset class, while multi-asset funds combine several within one portfolio.
Whether investments are held through an ISA, pension or another account, it is the underlying assets that determine much of the portfolio's investment behaviour.
An ISA or pension can provide particular tax treatment, while the investments held inside determine the market exposure and investment risk.
Investment planning
Does your current portfolio still match what the money is for?
A personal review can look through the funds and wrappers to the underlying asset allocation, risk, diversification, timeframe and role of the portfolio within your wider financial plan.
Book a conversationThis guide is for general information only and is not personal financial, investment or tax advice. Investments can fall as well as rise and you may get back less than you invest. Diversification does not guarantee against loss. Content checked against current FCA and MoneyHelper investment guidance on 16 September 2026.