Quick summary

The "crypto vs ISA" debate on TikTok is mostly framed wrong. It's not really a binary. The honest under-30 answer is roughly:

  • 0–5% of your investable wealth in crypto, if you genuinely want some, accepting it may go to zero
  • The other 95–100% in a diversified Stocks & Shares ISA holding global equity trackers

Why so cautious on crypto? Because the maths underneath the TikTok narratives doesn't actually work out the way they imply. Here's the honest comparison.

The TikTok claim, rephrased honestly

Typical TikTok finance content: "Forget ISAs — Bitcoin returned 230% last year. Why would you put money in a 7% ISA?"

The honest version of that claim: "Bitcoin returned 230% in one specific year. It also dropped 65% in another. Most people who put money in at the peak are still underwater. Most altcoins go to zero entirely."

Both versions are technically true. One sells courses. The other doesn't.

What the data actually shows

Bitcoin volatility (the largest, most established crypto)

Bitcoin's annual returns (illustrative — verify against current data):

  • 2020: +302%
  • 2021: +60%
  • 2022: -64%
  • 2023: +156%
  • 2024: +120%

That's a wild ride. If you bought at the peak of 2021 (~$69,000), you spent two years underwater before getting back. If you bought the bottom of 2022 (~$16,500), you tripled your money in two years.

The point: timing matters enormously with crypto, and no one — including the TikTok bros — can reliably predict it. Survivors talk loudly; the people who got wrecked don't post.

Global equity tracker (a typical S&S ISA holding)

Annual returns of the FTSE All-World Index:

  • 2020: +16%
  • 2021: +22%
  • 2022: -8%
  • 2023: +23%
  • 2024: +20%

Smoother. Less exciting. But over 5 years, you've roughly doubled your money with about a third of the drawdown risk.

Altcoins (anything that isn't Bitcoin or Ethereum)

Of the top 100 cryptocurrencies in 2017, only about 30 still exist in any meaningful form in 2026. The other 70 went to zero or near-zero — taking every penny invested with them. The 30 survivors have varied wildly.

For every Solana or Cardano that survived, there are 10 that became worthless. TikTok creators show you the survivors. They don't show you the ones they sold for a 95% loss two years ago.

The tax angle TikTok ignores

This is where the maths gets brutal for crypto:

Stocks & Shares ISA gains

  • No income tax on dividends
  • No capital gains tax on growth
  • No tax on withdrawals at any age

Buy a fund, hold for 30 years, sell — and the difference between what you paid and what you sold for is yours, every penny.

Crypto gains (outside an ISA)

You can't hold crypto in an ISA (it's not an HMRC-allowed asset). So all crypto sits outside the tax wrapper.

  • Capital Gains Tax applies on every gain above the £3,000 annual CGT allowance. At basic rate that's 10%; higher rate 20%. From April 2025 the rates increased for residential property but crypto rates stayed lower-band — verify current figures.
  • Income tax applies if you're seen as "trading" rather than "investing" (HMRC's distinction is fuzzy, but frequent trading triggers it)
  • Every trade is potentially a taxable event — even swapping one coin for another is a CGT disposal

So your crypto winner needs to first overcome the CGT bill before the after-tax return matches the ISA. A 30% crypto gain after CGT might be a 24% net gain. The "230% return" headline is always before tax in TikTok-land.

The honest under-30 framework

Here's how to think about it without the TikTok hype filter:

What's safe to allocate to crypto

A common framework from FCA-aware advisers:

No more than you can lose entirely without it affecting your life.

For most under-25s, that's probably £100–£500 total — money you wouldn't notice missing. Treat it as a learning expense / lottery ticket / cultural participation. Don't pretend it's investment.

For people with established financial bases (emergency fund + LISA + S&S ISA all on track), 0-5% of investable wealth in crypto is a reasonable speculation if you want it.

What's not OK

  • Putting your emergency fund in crypto
  • Borrowing to buy crypto
  • Putting your house deposit in crypto
  • Putting your entire savings in crypto because a creator said "this coin is the next 100x"
  • Skipping ISA contributions to "go all in" on crypto

These are the patterns that wreck young people's finances. They look bold; they're financially reckless.

The diversification argument

The strongest case for owning some Bitcoin specifically (not random altcoins):

  • It moves somewhat differently from equities — sometimes correlated, sometimes not
  • In a global financial crisis, it might hold value differently from stocks
  • It's the most established crypto with the longest track record

Even granting that, the academic research on Bitcoin-as-portfolio-diversifier suggests 5% maximum allocation for risk-balanced investors. Most TikTok creators recommending 50%+ in crypto are either trying to sell you something or are about to find out the hard way why diversification matters.

"But what about Solana / Ethereum / [new altcoin]?"

Same framework. Bitcoin is the only crypto with a 15+ year track record. Ethereum is 10+ but more technically experimental. Everything else is younger than your current pair of headphones.

If you want exposure to crypto-adjacent companies (mining, exchanges, custody), you can also do that via stock-market ETFs (e.g. iShares Blockchain ETF) — held inside an ISA, getting the tax wrapper benefit. That's a more boring but more wrapper-efficient way to get exposure to "blockchain succeeding" as a theme.

A realistic under-30 portfolio

For someone 25 with £5,000 to invest, no high-interest debt, emergency fund in place:

  • Allocation: Stocks & Shares ISA (global equity tracker) — Amount: £4,750 (95%) — Why: The wealth-building engine. Tax-free growth.
  • Allocation: Crypto (Bitcoin + Ethereum split) — Amount: £250 (5%) — Why: Speculation slice. Treat as the cost of cultural participation.

In 30 years:

  • The £4,750 ISA portion → roughly £36,000 at 7% nominal
  • The £250 crypto → unknowable. Could be £25,000. Could be £0. Both are within the realistic distribution.

Either way, the ISA is doing the work. The crypto is the wildcard.

What the FCA actually says

The Financial Conduct Authority's official position on crypto:

  • Not a regulated investment. If a crypto exchange collapses with your funds, you have no FSCS protection.
  • High risk of total loss. The FCA's own consumer warnings flag crypto as one of the highest-risk investments available to retail consumers.
  • Promotional rules tightened in 2023 — crypto firms now have to display warnings and cooling-off periods. There's a reason.

This doesn't mean crypto is bad. It means it's not in the same risk category as a diversified equity ISA, and any honest comparison has to acknowledge that.

What to do if you've already gone heavy on crypto

If you're 22 and 80% of your investable money is in crypto: you might be sitting on great paper gains and feel vindicated. Two things to consider:

  1. Crystallise some. Sell enough to use up your £3,000 CGT allowance (if you've held over a year), and put the proceeds into an ISA holding a global tracker. You can do this every tax year. Over time you de-risk without a single big tax event.
  2. Stop adding new money until you've also got an ISA in good shape. Continued contributions go to the ISA, not crypto, until the balance reflects 95/5 rather than 5/95.

This isn't anti-crypto. It's anti-undiversified.

Important

This article is general education, not personal financial advice. Crypto is a high-risk asset. Past performance is not a guide to future performance. For your situation, talk to an FCA-authorised independent financial adviser. Information on the FCA's crypto warning page is essential reading before any crypto purchase.

Related reading