Stocks and Shares ISA Balances Rise With Age, and the Mix Shifts Too

Bigger balances are the first thing that jumps out. HMRC data, obtained by MoneyWeek through a freedom of information request, shows that the average market value of a stocks and shares ISA rises steadily as people get older. The gap between the youngest and oldest savers is wide, and the reasons behind it say a lot about how long-term investing tends to work in practice.

Where average balances sit at each stage

Savers under 25 hold the smallest average amount, at £18,240. Those in their late twenties and early thirties average £41,060, and the 35 to 44 group sits at £68,500. The 45 to 54 band reaches £116,420, and balances keep climbing from there. Among people aged 85 and over, the average is £227,250, the highest figure in the dataset.

Source: HMRC, 11 November

Two forces explain most of the pattern. The first is income. Most people earn more as their careers progress, which leaves more room in the monthly budget for saving and investing. The second is time. Money left invested has longer to grow, and if markets have risen over that period, the shares originally bought are worth more. That second point depends on patience, though. The gains only show up for people who don't sell during a downturn, and that's easier said than done when a portfolio drops sharply.

It's worth remembering that an average can hide a lot. A mean figure is pulled up by a smaller number of large balances, and it doesn't tell you what a typical saver in any band actually holds. Think of the table as a picture of how balances tend to build over a working life, not a target to measure yourself against.

What people hold changes as they age

The size of a portfolio isn't the only thing that shifts. The types of investments people favour appear to change too. Hargreaves Lansdown's data suggests that younger investors lean toward exchange-traded funds (ETFs) and tracker funds, while older investors tend to hold investment trusts, gilts and cash ISAs.

Kate Marshall, head of fund research at Hargreaves Lansdown, framed the difference this way: the data is "less about one investment being better than another and more about what people need from their money at the time." That's a useful lens. A product that suits someone with four decades ahead of them may do a different job for someone who needs income next year.

The ETF and tracker pattern is especially clear. Around 70% of ETF and tracker fund holders on the platform are under 55, while only 6% and 7% respectively are over 75. Marshall linked that to time horizon. "When retirement is decades away, time is your biggest asset," she said. Growth-focused holdings, such as global equities, can recover from downturns given enough years, and simpler, lower-cost funds offer a relatively straightforward way to spread money across a broad range of markets. That's the appeal for someone starting out, though a broad fund still rises and falls with the market it tracks.

Why mid-life investors reach further abroad

Investors in their 30s, 40s and 50s show a different habit. They buy more overseas shares, and people aged 35 to 54 make up nearly half of Hargreaves Lansdown's total owners of this type of holding. Marshall suggested this could reflect more established portfolios, a greater willingness to look beyond the UK, or a view of where growth might come from. Her point was that international investing gives access to companies and sectors the UK market doesn't offer in the same way.

My read is that this is where the trade-offs get interesting. Overseas exposure adds diversification, but it also brings currency movements and different market rules into the mix. Someone building a portfolio at this stage should weigh those factors against their own goals rather than follow a headline trend.

Shifting toward stability as retirement nears

Priorities tend to change again as retirement comes into view. People start paying closer attention to how their savings will support them once they stop working. Marshall said that as the time horizon shortens, it's understandable to dial back on higher-risk assets like equities and introduce holdings that offer steadier returns or pay income alongside growth.

The age profile of different products reflects that shift. Gilt and cash ISA holders skew older, with 42% and 41% respectively in the 55 to 74 bracket. Investment trust holders are older still: 57% are 55 or over, and 19% are 75 or over. Marshall suggested part of the reason is that many investment trusts have built records of paying and growing income over time. Their closed-ended structure also gives managers more room to invest for the long term, which can appeal to anyone balancing growth, income and diversification as retirement approaches.

Here's the thing: the pattern of taking more risk when young and moving toward safer holdings later is a common shape, not a rule. Plenty of people hold equities well into retirement, and some keep a larger cash cushion earlier in life. What matters is whether the mix suits your goals, your timeline and how much volatility you can live with without panic selling.

If you're reviewing your own ISA, the useful question is less "what should a person my age hold?" and more "what is this money for, and when will I need it?" Start there, and the age-based averages become a helpful reference rather than a script. Marshall's own summary captures it well: portfolios often evolve gradually, and keeping the balance matched to your goals, time horizon and attitude to risk is the part that counts.