You can lose money in a stocks and shares ISA. You can’t realistically lose all of it — unless you do one of three specific things, and all three are avoidable.
Most people typing this question don’t mean “what if I have a bad year?” They mean “what if it all disappears?” Different question, and it has a real answer.
The ISA isn’t the thing at risk
A stocks and shares ISA isn’t an investment, whatever the name suggests. It’s a wrapper — a tax-free box the government lets you put investments inside. The box itself can’t lose you anything.
What determines your risk is what you put in the box. Put in a fund that owns 500 of the biggest companies in America, or thousands of companies across the whole world, and your risk is the market’s ups and downs. Put in shares of one exciting company, and your risk is that company. Same ISA, completely different question.
What happens when the market crashes?
Crashes happen. Roughly once a decade the market falls hard, it’s on every front page, and it feels like the end of the world.
The unluckiest index investor in modern history bought the S&P 500 at its October 2007 peak — 1,565 — the very top, the day before the financial crisis began. By March 2009 his money had fallen 57%. It took about five and a half years to get back to where he started.
And today? The S&P 500 closed above 7,600 last night. That worst-possible-timing investor is sitting on nearly five times his money — before counting dividends. Bought at the top, held through the worst crash since 1929, and still made about 8.7% a year.
For a fund holding 500 of the world’s biggest companies to go to zero, every one of them has to be worth nothing on the same day. That isn’t a market crash — it’s the end of the economy, and at that point your cash is worthless too.
The real risk in a crash isn’t the fall. It’s you, selling during it. The people who turned 2008’s temporary 57% into a permanent loss were the ones who sold at the bottom. The market gave the money back to everyone who stayed.
I can’t tell you when the next crash is coming. Neither can anyone else — the people who claim they can are selling something. What I can tell you is what every crash so far has had in common: lower prices for a while, then higher prices than before.
What happens if my platform goes bust?
This is the other version of the fear — not the market failing, but the app failing. This one has a real safety net.
Your investments don’t belong to the platform. They’re held separately, in what’s called a nominee account, ring-fenced from the platform’s own money. If the platform goes under, your shares and funds are still yours — they get transferred to another provider or returned to you. The administrators can’t use your Apple shares to pay the platform’s debts.
And if something has gone badly wrong in that process — fraud, missing assets — the FSCS covers investment claims up to £85,000 per person, per firm. (That’s the investment limit. The better-known limit for cash in banks went up to £120,000 in December 2025 — different scheme, different thing.)
What the FSCS doesn’t cover is the market going down. It doesn’t need to. A fall in the market isn’t your money being taken — it’s a price change on things you still own.
How people actually lose everything
Because it does happen — just not the way the fear imagines. Three ways, all avoidable:
Owning one company. Single shares can go to zero. Carillion shareholders got nothing. If your whole ISA is one stock, total loss is a real possibility. A fund that owns hundreds of companies takes that off the table.
Scams. Nobody legitimate is offering you a guaranteed 12%. The word “guaranteed” attached to a high return is the whole warning.
Selling at the bottom. The self-inflicted one — turning a temporary fall into a permanent loss because holding on felt unbearable. This is a fear problem, not a market problem, and I’ve written about the fear itself, taken seriously.
Avoid those three and the realistic worst case isn’t “it’s all gone.” It’s “it’s worth less for a few years, and you have to leave it alone.”
So what do I actually do with this?
If your money is sitting in a cash ISA earning less than inflation because this fear had you frozen — that’s the trap working as designed. Here’s how a cash ISA and a stocks and shares ISA actually compare, and when you’re ready, the boring index fund is the first thing to buy.
You can lose money in a stocks and shares ISA. But nobody has ever lost everything in a global index fund — and the worst-timed buyer in stock-market history ended up with five times his money.
This is what I write about every week — managing your own money without paying someone 1–2% a year to do it worse. The letter is free.
I am not a financial adviser. Nothing here is personal financial advice. This is my own experience and opinion, shared for information and education. Investing involves risk — the value of investments can fall as well as rise, and you may get back less than you put in. Please do your own research before acting.