What to actually invest in your ISA
You've opened a Stocks and Shares ISA — or you're about to. The tax wrapper is sorted. But the question that stops most people in their tracks is: what do I actually buy?
The finance industry has a habit of making this feel impossibly complicated. There are thousands of funds, hundreds of platforms, and no shortage of people with strong opinions about which sectors are about to boom. Most of it is noise.
For the vast majority of UK beginners, the answer is remarkably simple: one global index fund, bought regularly, held for years. This guide explains what that means, which one to pick, and why this approach has outperformed most professional fund managers over the long run.
You have until midnight on 5 April 2027 to use this year's £20,000 ISA allowance. Money deposited before that date grows tax-free forever. After 5 April, that allowance is gone — you can't carry it forward.
What is an index fund?
Most investments are actively managed — a fund manager tries to pick the stocks they think will go up. They charge a fee for this effort. And decades of evidence show that the majority of them fail to beat the market over the long term, especially after fees.
An index fund takes the opposite approach. Instead of trying to pick winners, it simply owns everything in a given market. If the index goes up by 8%, the fund goes up by 8% (minus a tiny fee). There's no guessing, no research, no complexity. It just mirrors the market.
The FTSE 100 is an index of the 100 largest companies listed on the London Stock Exchange. The S&P 500 is an index of 500 of the largest US companies. The MSCI World covers around 1,500 companies across 23 developed countries. A global all-world index stretches to over 3,000 companies across both developed and emerging markets.
When you invest in a global index fund, you're not betting on any one company or country. You're betting that the global economy, across all its companies and sectors, will be worth more in 20 years than it is today. It's a long bet. But it's a historically well-supported one. The value of investments can fall as well as rise — you may get back less than you invest.
That fee difference sounds small. But over 30 years, paying 0.75% per year versus 0.12% on a £100,000 portfolio costs you roughly £60,000 in lost returns. Index funds win on cost before they even start.
Why global, not just UK
It's tempting to invest in what you know. The FTSE 100 is familiar — Barclays, Tesco, BP. But the UK stock market represents only around 4% of the world's total market value. Investing only in the UK means ignoring 96% of the world's publicly traded companies.
A global fund gives you exposure to US tech giants, European industrial companies, Japanese exporters, South Korean manufacturers, Indian banks, and everything in between. When one region struggles, others may compensate. That's real diversification.
This is why most UK personal finance communities — including the widely followed r/UKPersonalFinance wiki — recommend a global tracker as the default starting point, rather than a UK-focused fund.
Index funds vs ETFs — what's the difference?
You'll encounter both terms. The distinction matters less than you think, but it's worth understanding.
A traditional index fund (also called a unit trust or OEIC) is priced once per day. You buy units from the fund manager at the end-of-day price. It's simple, hands-off, and requires no trading knowledge.
An ETF (Exchange-Traded Fund) works similarly — it tracks an index — but it trades on a stock exchange like a share. The price moves throughout the day. You can buy and sell at any point during market hours.
For a long-term monthly investor putting money into an ISA and leaving it there, this difference is almost irrelevant. You're not trying to time the market. The choice between the two mainly comes down to which platform you're using and what's available with the lowest cost on that platform.
On platforms like Trading 212 and InvestEngine, ETFs are free to trade and very well suited to monthly investing. On Vanguard, the index funds (not ETFs) are slightly easier to use and come with automatic monthly investment. Both approaches work — the fund type matters far less than the fee and how consistently you invest.
Accumulation vs Income — always choose Acc
At the end of most fund names you'll see either Acc (Accumulation) or Inc (Income). This tells you what happens to dividends — cash payments that companies make to their shareholders.
An Acc fund automatically reinvests those dividends back into the fund. The money stays invested and compounds. You don't need to do anything.
An Inc fund pays dividends out to you as cash. That sounds nice, but inside an ISA where you don't need the cash right now, it means those dividends sit idle until you manually reinvest them — slowing down your compounding.
For most long-term ISA investors, the Accumulation share class is the more appropriate choice. It reinvests dividends automatically — compounding works better when nothing interrupts it. Consider Income (Inc) if you need cash distributions.
Which fund should I actually buy?
Here are the three most widely recommended options among UK beginner investors. All three are globally diversified, low-cost, and suitable for holding inside a Stocks and Shares ISA.
If you're on Vanguard: the Vanguard FTSE Global All Cap is a strong option. If you're on any other platform: the HSBC FTSE All-World gives you near-identical coverage at a lower fee. If you're already on Fidelity: the Fidelity Index World is perfectly fine. All three are excellent. The fee matters more than which one you pick.
Fee comparison across the main options
| Fund | Index tracked | OCF | Holdings | Incl. EM |
|---|---|---|---|---|
| HSBC FTSE All-World Index Fund | FTSE All-World | 0.12% | ~3,000 | Yes |
| Fidelity Index World Fund | MSCI World | 0.12% | ~1,500 | No |
| Vanguard FTSE Global All Cap | FTSE Global All Cap | 0.23% | ~7,000 | Yes |
| Vanguard LifeStrategy 100% | Multi-index blend | 0.22% | ~7,500 | Yes |
| Typical active managed fund | Manager's picks | 0.75%+ | Varies | Varies |
Row highlighted in green = the option most commonly cited by UK personal finance communities for beginners based on cost and coverage.
What about Vanguard LifeStrategy?
You'll often see LifeStrategy funds recommended for beginners. They're a single fund that bundles equities and bonds together in a fixed ratio — LifeStrategy 80% is 80% stocks, 20% bonds. They rebalance automatically and are genuinely simple to use.
The catch is that LifeStrategy funds have a significant home bias — they allocate around 20% of the equity portion to UK stocks, far higher than the UK's actual 4–5% share of global markets. This is deliberate, not accidental, but it means your portfolio is concentrated in the UK more than a truly global tracker would be.
For a long-term ISA investor who wants maximum simplicity and doesn't mind the UK tilt, LifeStrategy 100% is a perfectly reasonable choice. For those who prefer to track global market weights, the HSBC or Vanguard Global All Cap options above are more appropriate.
How much do I need to start?
Much less than most people assume.
The tax year deadline is 5 April. Even depositing £50 or £100 before then uses some of your allowance within this tax year — meaning that money grows inside the ISA wrapper from day one. There's no prize for waiting.
How to actually do this
Open a Stocks and Shares ISA
If you haven't already, choose a platform. For beginners investing in ETFs: Trading 212 or InvestEngine (no platform fee). For index funds and simplicity: Vanguard. See our full ISA guide for a detailed comparison.
Search for the fund
Inside your platform, search for your chosen fund by name — "HSBC FTSE All World" or "Vanguard Global All Cap". Make sure you select the Acc (Accumulation) share class, not Inc.
Set up a monthly direct debit
Most platforms let you set up a recurring investment — the same amount invested on the same day each month. This is called pound-cost averaging: you automatically buy more units when prices are low and fewer when prices are high. It removes the temptation to time the market.
Don't touch it
The hard part. Index funds reward patience. The biggest mistake most investors make is selling during a market dip — crystallising a loss instead of waiting for recovery. Set a reminder to check in once per year at most. Otherwise, leave it alone.
Common myths that stop people starting
What to expect over time
Index funds go up and down. Sometimes sharply. The global market fell around 30% in a matter of weeks in early 2020. It recovered within months. It fell again in 2022. It recovered again. Over any 20-year period in modern history, a global index has produced positive real returns.
This is not a promise that the future will resemble the past. Markets can and do disappoint. But the alternative — keeping long-term money in cash — guarantees that inflation erodes its value year by year.
Illustrative only. Investment returns are not guaranteed and the value of investments can fall as well as rise. Past performance is not a reliable indicator of future results.
Investing involves risk. The value of your investments can go down as well as up, and you may get back less than you put in. Index funds are not suitable for money you may need within the next five years. This is not personal financial advice — if you're unsure what's right for your situation, consider speaking to a regulated financial adviser.
What comes after this
Once you've started investing in a global index fund inside your ISA, the next step in the Eight Steps framework is to make sure you're also contributing enough to your pension — ideally up to 15% of your salary. Your employer pension and your ISA work together: the pension gives you tax relief on the way in, the ISA gives you tax-free access on the way out.
The tax year ends on 5 April 2027. This year's £20,000 ISA allowance cannot be carried forward. Start here →