How To Become An ISA Millionaire? What You Need To Know!

To become an ISA millionaire, most people need to invest close to the full £20,000 allowance every year (about £1,667 a month) in a stocks and shares ISA for 20 to 28 years, depending on how their investments grow. At an example 5% a year that’s about 25 years; at 8% it’s about 20. Growth isn’t guaranteed, and investments can fall as well as rise, but it’s been done: HMRC figures show 7,730 people had ISAs worth £1 million or more in 2023/24.

Budget update, 28 October 2026: nothing in the latest Budget touches the route to an ISA million. The £20,000 allowance stays, the planned cash ISA cut has been scrapped, and stocks and shares ISAs are unchanged.

What makes an ISA millionaire?

Simply put, it’s someone with £1 million or more in their ISAs. With a maximum of £20,000 a year going in, an ISA millionaire is someone who has saved and invested regularly for a long time, usually maxing out their allowance, and stuck with it through the ups and downs. If you want the bigger picture beyond ISAs, I’ve written about how to become a millionaire in the UK.

As humans, we’re obsessed with the £1 million mark. It has this magical weight that when we get there, we’ve made it: foot off the gas and piña colada in hand. When I talk to friends and family, a lot of people think ISAs are mythical creatures only people in suits understand. That couldn’t be further from the truth. ISAs are pretty straightforward.

There are broadly two ways people try to get there: slow and steady, or hard and aggressive. The aggressive route, betting big on a handful of shares, also needs a lot of luck. A balanced, diversified approach held for decades is how most people get there.

How long does it take to become an ISA millionaire?

It depends on how much you put in and how your investments grow. Here’s the full £20,000 a year, paid in monthly, at different example growth rates. These are illustrations, not predictions. The growth rates are after fees, and inflation isn’t included.

You’ll sometimes read that you can do it in 20 years at 6%. You can’t: at 6% a year you’d have about £770,000 after 20 years. Small differences in growth make a big difference over decades, which is why fees and time matter so much.

What if you can’t invest £20,000 a year?

Most people can’t, and that’s fine. Here’s what different monthly amounts could grow to, again with example growth rates:

Growth isn’t guaranteed. Real investments don’t grow in a straight line, and some years they’ll fall. But the table shows the point: even if you never reach a million, regular investing can build a pot that changes your life.

So, what is an ISA?

An ISA (individual savings account) is a tax-free wrapper for saving or investing. You pay no income tax on interest, no dividend tax and no Capital Gains Tax on anything inside it, and you can take money out whenever you like. You can put in up to £20,000 a year, split across cash, stocks and shares, Lifetime and innovative finance ISAs. Read my full guide to what an ISA is and each type.

For an ISA million, the stocks and shares ISA does the heavy lifting. The tax-free part matters more the bigger your pot gets: on a £1 million portfolio outside an ISA, dividends above £500 a year and gains above £3,000 a year would be taxed.

What the 2027 ISA Changes Mean for Your Million

You may have read that the cash ISA allowance was dropping to £12,000 for under-65s from April 2027, with a new charge on cash sitting in stocks and shares ISAs and a ban on moving stocks and shares ISAs into cash. The 28 October 2026 Budget scrapped all of that.

• The overall ISA allowance stays at £20,000 a year, and you can still put all of it into a stocks and shares ISA.
• The cash ISA limit stays at £20,000 for everyone 18 and over.
• No charge on cash held in your stocks and shares ISA, and you can still transfer in either direction.
• The government plans a new incentive for people investing in a stocks and shares ISA for the first time. There are no details yet.

The core message hasn’t changed: use as much of your £20,000 as you can, lean on a stocks and shares ISA for long-term growth, and let compounding do the work. Every change is explained in my guide to the 2027 ISA changes.

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How to become an ISA millionaire: 5 top tips

These five habits are what most long-term investors have in common. Nail them and you give yourself a real shot.

1. Create a budget

It all starts with a budget. If you’re going to invest regularly, and especially if you want to get anywhere near the £1,667 a month it takes to max out your ISA, you’ll need a damn good one. You can use a spreadsheet, the notes on your phone, an app, or our budgeting calculator. If you’re like me, you’ll want something you can edit quickly.

To get good at budgeting you need to know what’s coming in and what’s going out. Then look for savings: you’ll find small wins and be inspired to renegotiate your bills. Put the money you save towards your ISA. Don’t suddenly go wild on ASOS!

2. Maximise your contributions

The £20,000 mark is the goal, but for most of us it’s unrealistic. The median full-time salary in the UK is £40,911 before tax, so investing £20,000 a year would mean living in a tent eating cold beans. Not likely.

If you’ve nailed your budget, though, you’ll have found money to put in. Investing as much as you can without wrecking your lifestyle shortens the journey, and starting early helps even more. When I started, I was putting just £25 a month into my ISA as I was clearing debt. Once I saw it grow, I doubled down and kept increasing it.

For context, £25 a month for 30 years is £9,000 paid in. At an example 5% a year it could grow to about £20,806, and at 8% about £37,259. Not a million, but proof that small amounts add up, and it’s the habit that counts. Raising your monthly amount every time you get a pay rise is how you close the gap.

Couples have an advantage here: you each get your own £20,000 allowance, because ISAs can’t be held jointly. Two people each investing the full amount at an example 5% a year would reach £1 million between them in about 16 years.

3. Use a stocks and shares ISA

This is key. If you only use a cash ISA, it’s very hard to become a millionaire because cash usually grows far more slowly over the long term. A 2025 Freedom of Information request reported by MoneyWeek found no ISA millionaires had got there with cash ISAs alone in 2021/22; 94% held only stocks and shares ISAs.

With Bank Rate at 4%, cash ISAs pay a decent rate right now, and they’re the right home for your emergency fund and short-term goals. But for money you can leave for 20 years or more, investing has historically given a better chance of growth, with the risk that the value can fall. I compare the two in cash ISA vs stocks and shares ISA, and explain the mechanics in how a stocks and shares ISA works.

When you invest, your capital is at risk.

4. Pick a strategy you can stick to

It’s up to you what goes inside your stocks and shares ISA, so start by understanding how much risk you can handle. Ask yourself how you’d feel if your pot dropped by a fifth in a bad year. Many long-term investors keep it simple with low-cost index funds or ETFs that spread money across hundreds or thousands of companies, rather than trying to pick winners. Here’s how index funds work in the UK.

Reinvesting your dividends (the share of profits companies pay out) helps too, because those payments then earn returns of their own. Many funds have an “accumulation” version that does this automatically.

Fees matter more than most people think. Here’s the full £20,000 a year for 25 years, assuming investments grow 6% a year before fees:

That 0.8% difference costs about £128,000 over 25 years. If you’d rather not pick investments yourself, ready-made and managed ISAs will do it for you for a fee. If you’re unsure, a regulated financial adviser can help you build a plan.

5. Be patient

This is the most underrated tip. You need time more than anything else, and the discipline to keep investing when markets fall and not to dip into your pot. Most ISA millionaires have been investing for decades. We talked about the habits of ISA millionaires with Holly Guscott on The Money Gains Podcast.

A couple of other things can speed up the journey. Some people invest their lump sum at the start of the tax year rather than spreading it out, so it has longer to grow, although that means more of it is exposed if markets fall early on. And if you’re 18 to 39, a Lifetime ISA adds a 25% bonus on up to £4,000 a year, but that money is meant for a first home or for after 60, with a charge if you take it out for anything else.

What do I have to do to become an ISA millionaire?

• Budget like a pro
• Find savings and efficiencies in your budget
• Start investing, even if it’s small, and increase it over time
• Open a stocks and shares ISA and choose a diversified, low-cost approach you understand
• Work towards maxing out your contributions
• Leave it alone and keep paying in for 20 years or more
• Wahooooo, you’re a millionaire!

How many ISA millionaires are there in the UK?

7,730 people had ISAs worth £1 million or more in the 2023/24 tax year, according to HMRC data released to the savings app Plum under a Freedom of Information request. That’s up from 5,070 the year before, a record jump of more than 50% in a single year.

For context, 23 million adults held an ISA in 2023/24, and 28.8% of people who paid into an ISA that year paid in the full amount. So ISA millionaires are a tiny group, but a fast-growing one, because the people who’ve been maxing out their allowance for 20 years or more are now reaching the million.

Now I’m an ISA millionaire, then what?

Once you’ve got there, protecting your wealth matters as much as growing it. You don’t want to flick a switch and start blowing it.

Everything you take out of an ISA is tax-free. As an example, taking 3% a year from £1 million would give you £30,000, and 4% would give you £40,000, with no income tax to pay. Whether that lasts depends on how your investments do, so it isn’t guaranteed. Compare that with a pension, where most withdrawals beyond the tax-free lump sum are taxed as income; I explain the trade-offs in SIPP vs ISA. And here’s how much interest £1 million could earn.

ISAs do still count towards your estate for inheritance tax when you die. If you leave your ISA to a spouse or civil partner, they get an extra one-off ISA allowance worth up to its value, so it can stay tax-free.

ISA Millionaire FAQs

Conclusion

The road to becoming an ISA millionaire is long, but tax-free growth is something we should all consider. We pay enough in income tax, so why give up more?

The most important thing is to get started, even if it’s just £25 a month. Save, invest, be patient, and your ISA could become the thing that makes you financially free.