I am not a financial advisor and nothing in this post constitutes financial advice. All investments carry risk and the value of your investments can go down as well as up. Please do your own research and consider seeking independent financial advice before making any investment decisions.
Introduction.
If you’ve opened a platform comparison table recently, you’ll know the problem. Six platform names across the top, a dozen rows of percentages and dealing charges underneath, all technically accurate and none of it telling you what you actually want to know: which one is right for someone in your position, with your portfolio, at this stage of your life.
That’s not a gap in your knowledge. It’s a gap in how these comparisons get built. Most of them are written by someone who has never actually held a SIPP through a bad month, never sat there watching a flat fee slowly overtake a percentage fee as their own portfolio grew, never had to weigh up whether consolidating five accounts under one login was genuinely worth the effort of switching. They’re accurate on paper. They just weren’t lived by whoever wrote them.
I’m Angelina, and I have lived this one. Seven years ago I opened a stocks and shares ISA with Interactive Investor, followed not long after by a SIPP, then a trading account, then two Junior ISAs for my children once my father gifted them some money to invest. Five accounts, one platform, seven years of decisions made with real money sitting in real markets, not hypothetical numbers on someone else’s spreadsheet.
So when I tell you that a flat fee only beats a percentage fee once your portfolio crosses a certain size, I’m not repeating something I read on a fee schedule. I watched it happen with my own money, in my own account, over a number of years. I’ve been the version of you that’s putting this decision off, the one that closes the tab because none of it quite adds up to an answer yet. I’ve also felt what it’s like on the other side of that decision, seven years in, looking back and being glad I made it when I did.
This guide walks you through six of the platforms UK investors talk about most, and it tells you honestly which one is the best stocks and shares ISA UK depending on where you actually are right now, your portfolio size, your stage of life, what you’re trying to build. Not a generic answer that pretends one platform suits everyone.
Let’s get into it.
What is a stocks and shares ISA.
A stocks and shares ISA is simply a tax wrapper. It doesn’t decide what you invest in or how, it just sits around your investments and shelters any growth from tax. Sell an investment at a profit outside an ISA and capital gains tax can apply. Hold it inside one and that profit is entirely yours. The same goes for dividends, which are normally taxed once you’re above your dividend allowance, but not inside a stocks and shares ISA. You get £20,000 to put into ISAs each tax year, across however many ISA types you use, and that allowance resets every April whether you use it or not.
The distinction that trips people up is the one between a cash ISA and a stocks and shares ISA. A cash ISA is essentially a savings account with tax free interest, low risk, low return, and largely eroded by inflation over time. A stocks and shares ISA puts your money into the market instead, funds, shares, ETFs, which carries real risk of loss but has historically outperformed cash by a wide margin over the long run. If you’re still deciding whether you’re ready to make that move from saving to investing, my How To Start Investing guide covers that groundwork in more detail before you get into platform comparisons like this one.
Who should open one.
A stocks and shares ISA isn’t the right first move for everyone, and any guide that skips past this to get to the exciting platform comparisons isn’t doing you any favours. Before you open one, it’s worth checking you’re actually ready.
You have an emergency fund in place. Three to six months of essential expenses sitting in an easy access savings account, untouched. Investments can and do fall in value, sometimes sharply, and you don’t want to be forced to sell at a loss because your boiler’s just packed in and you need the cash by Friday.
You’ve cleared any high interest debt. If you’re carrying credit card debt or a loan charging anything close to double digit interest, paying that off first is the better use of your money. No stocks and shares ISA is reliably going to outperform an 18% credit card rate. Clear the debt, then invest what’s left.
This is money you won’t need for at least five years. Markets go up over the long term, but the short term can be genuinely rough. Five years is a reasonable minimum horizon to give your investments room to recover from a downturn without you having to sell at the wrong moment. If you might need this money next year for a house deposit or a wedding, even the best stocks and shares ISA UK isn’t the right home for it.
You understand you could lose money. This sounds obvious written down, but it’s worth saying plainly. Investing isn’t saving. Your capital is at risk, and the value of your ISA can go down as well as up.
I know this one from experience, not just theory. During the Covid lockdown I watched the value of my own investments drop further and faster than I’d ever seen. That was a genuine stay calm moment, the kind where every instinct tells you to sell and get out. I didn’t. I left it invested, and over time it recovered but the mild panic I felt through that whole period was a real squeaky bum moment. Historically, that’s what markets have done, recovered, given enough time and enough patience not to sell at the bottom. It’s not a guarantee for the future, nothing in investing is, but it’s exactly the kind of moment this checklist is trying to prepare you for before it happens to you.
If all four of those are true for you, you’re in a sensible position to open a stocks and shares ISA. If one or two aren’t quite there yet, that’s useful information too. Get those in order first, and the ISA will still be waiting for you.
How to choose the best stocks and shares ISA UK for you.
There isn’t a single best stocks and shares ISA. There’s a best one for you, at your stage, with your portfolio and your priorities. This section is where I break down the four things that actually determine which platform wins for you, rather than which one wins in the abstract.
Fee structure: flat fee versus percentage fee
This is the single decision most people get wrong, because it looks like a small technical detail and it is actually the thing that determines how much of your money stays invested rather than disappearing into charges every year.
A percentage fee platform, think Hargreaves Lansdown, Fidelity, AJ Bell, Vanguard, charges you a set percentage of your total portfolio value annually. That fee grows every single year alongside your investments. A flat fee platform, Interactive Investor is the clearest UK example, charges you the same amount regardless of how large your portfolio becomes.
Here’s what that looks like in real terms, comparing Hargreaves Lansdown’s 0.35% charge against Interactive Investor’s Core plan:
- At £50,000, HL costs £175 a year. Interactive Investor costs £71.88.
- At £77,000, HL costs £269.50 a year. Interactive Investor still costs £71.88.
- At £100,000, HL costs £350 a year. Interactive Investor still costs £71.88, right up to the point your total portfolio crosses that threshold and you’d move to the £14.99 a month Plus plan.
Let those numbers sit for a second. At £100,000, you’re looking at a gap of £278.12 a year between the two platforms, for genuinely comparable access to a stocks and shares ISA. That’s not a rounding difference. That’s money that either compounds inside your portfolio for the next twenty years, or gets paid out in fees every single year regardless of how your investments perform.
The flip side matters too. At smaller portfolio sizes, percentage fees are often cheaper, which is exactly what we saw in the three reader scenarios earlier in this post. There’s no universally cheaper model. There’s a crossover point, and knowing roughly where it sits for your own numbers is the most useful thing this section can give you.
Account types needed
If a stocks and shares ISA is the only account you’ll ever want, your shortlist looks different from someone who also wants a SIPP, a Junior ISA for their children, or a general trading account alongside it.
Some platforms genuinely shine as ISA only options, Trading 212 among them, with no platform fee at all. But if you know you’ll want to consolidate a pension into a SIPP in a few years, or you’re likely to open Junior ISAs for children down the line, it’s worth choosing a platform that handles all of those well from day one, rather than an ISA specialist you’ll outgrow and have to migrate away from later. Migrating investments between platforms is possible, but it’s rarely as simple as it sounds on the tin, so it pays to think a step or two ahead.
Investment choice
Every platform will tell you how many thousands of funds and shares it offers, as though breadth alone is the differentiator. For a lot of investors, particularly anyone planning to build a portfolio around one or two global index funds, it genuinely isn’t.
If your entire strategy is a single global tracker fund, held monthly and left alone, a platform with 40,000 investment options offers you nothing that a platform with 5,000 doesn’t. What matters far more is whether the specific fund or funds you actually want to hold are available on the platform you choose, and whether the cost of holding them stays low. Breadth matters enormously if you’re an active stock picker exploring international markets. It matters not a jot if you’re building a simple, low cost, diversified portfolio and leaving it to grow.
Ease of use
This one gets underweighted in most comparisons, and it shouldn’t be. A platform that feels confusing or cluttered tends to produce one of two bad outcomes. Either you check it constantly out of anxiety, second guessing every dip and every rise, or you avoid logging in altogether and lose track of what’s actually happening with your money.
Neither of those is a healthy relationship with your own investments. The right platform for you is one where checking in feels calm rather than stressful, where you can see what you hold and how it’s performing without hunting for it, and where the app or website doesn’t nudge you toward the kind of frequent trading that quietly erodes long term returns. This is genuinely personal. What feels intuitive to one investor feels cluttered to another, so where possible, look at screenshots or try a demo before committing.
The platforms compared.
| Platform | Fee Model | ISA Annual Cost | SIPP Annual Cost | Fund Dealing | Share Dealing | Best For |
| Vanguard | Percentage | 0.15%, capped at £375/year | Same | Free | £7.50 (Quote and Deal only) | Fund investors under £250k who want Vanguard funds only |
| AJ Bell | Percentage | 0.25%, capped at £42/year (shares) | 0.25%, capped at £120/year | £1.50 | £5, or £3.50 with 10+ deals | ETF and share investors who want a fee cap |
| Trading 212 | Zero platform fee | Free | Free (SIPP in beta) | Free | Free | ETF investors wanting the lowest possible cost. Note: SIPP in beta, no drawdown available yet. Not suitable as a sole retirement platform. |
| Fidelity | Percentage | 0.35%, capped at £90/year (shares) | Same tiers | Free (funds) | £7.50 (shares) | Fund investors who want broad choice |
| Hargreaves Lansdown | Percentage | 0.35%, capped at £150/year (shares) | 0.35%, capped at £150/year | £1.95 | £6.95 | Investors who want phone support and broad choice |
| Interactive Investor | Flat fee | Included in £5.99 or £14.99/month Plus Plan | Free | £1.49 | £3.99 (Free monthly trade with Plus Plan) | Investors with multiple accounts or larger portfolios |
A Closer Look At Each Platform
Interactive Investor
I’ve used Interactive Investor for seven years, and it remains the platform I’d choose again today without hesitation. It’s a flat fee platform, £5.99 a month on the Core plan for a total portfolio up to £100,000, rising to £14.99 on Plus above that threshold, and that single fee covers your stocks and shares ISA, your SIPP, and a trading account together, with no extra charge for holding more than one.
The genuine strength here is exactly what the fee comparisons above show. Once your portfolio starts to grow, particularly past the £50,000 mark, the flat fee pulls ahead of every percentage based competitor on this list, and the gap only widens from there. The genuine weakness is the flip side of the same coin: if you’re starting out with a smaller pot, that flat fee is more expensive than a percentage fee would be, and it stays that way until your portfolio catches up.
I’ve written a full, honest breakdown of my seven years with Interactive Investor, including what the SIPP has actually been like to manage and what I’d tell you before you open one, in my Interactive Investor Review 2026.
Hargreaves Lansdown
Hargreaves Lansdown is the UK’s largest investment platform, and it charges a percentage fee of 0.35% on your ISA and SIPP, capped at £150 a year for shares, ETFs and investment trusts, with a £1.95 charge to deal funds.
Its clearest strength, even in a year of considerable upheaval for the platform, is phone based customer support. Even in HL’s most critical Trustpilot reviews, the people answering the phones are consistently praised, which matters if you want a knowledgeable human to talk to while you’re still finding your feet. Its clearest weakness right now is cost at scale. Above roughly £50,000 combined across an ISA and SIPP, HL’s percentage fee starts to compound noticeably against flat fee alternatives, and that gap only grows as your portfolio does.
I’ve covered HL’s fees, its recent ownership change, and what its Trustpilot data actually shows in far more depth in my Hargreaves Lansdown Review 2026.
Fidelity
Fidelity charges 0.35% on your ISA and SIPP, but with a meaningful difference from HL: the fee on shares and ETFs is capped at £90 a year rather than £150, and fund dealing is free.
The strength here is that £90 cap. Once your shares and ETFs inside an ISA or SIPP reach around £25,700, the cost of holding them stops growing entirely, which makes Fidelity structurally cheaper than Hargreaves Lansdown for anyone building a larger ETF heavy portfolio. The weakness is share dealing cost. At £7.50 a trade, it’s the most expensive share dealing charge of any platform on this list, so Fidelity suits a fund investor who wants broad choice far more than it suits someone who deals in individual shares regularly.
Vanguard
Vanguard charges 0.15% across your ISA and SIPP, capped at £375 a year, with free fund dealing and a £7.50 charge only if you use its optional Quote and Deal service for ETFs.
It’s genuinely one of the cheapest percentage fee platforms in the UK, and the simplest starting point if you’re happy investing exclusively in Vanguard’s own range of funds. That’s also its limitation: your choice is confined to Vanguard funds, so if you want access to a wider universe of shares and funds from other providers, this isn’t the platform for that. You can find full details on Vanguard’s own site.
AJ Bell
AJ Bell charges 0.25%, with shares in an ISA capped at £42 a year and shares in a SIPP capped at £120 a year, alongside a £1.50 fund dealing charge and £5 share dealing, dropping to £3.50 if you make ten or more trades in a month.
It sits neatly between Vanguard and the larger percentage platforms on cost, and its low ISA share cap makes it particularly competitive for anyone holding ETFs rather than funds. Full details are on AJ Bell’s charges page.
Trading 212
Trading 212 charges no platform fee at all on its ISA, with free fund and share dealing. Its SIPP is currently in beta, also free, though it doesn’t yet offer drawdown, which matters if you’re closer to actually accessing your pension than building it. For the cheapest possible way to run a straightforward ISA, it’s worth knowing about, even if it isn’t yet a complete platform for every account type you might eventually need.
If you are just starting out with under £20,000
At £10,000, a stocks and shares ISA invested in a straightforward index fund, the cheapest option by a distance is Trading 212, which charges nothing at all: no platform fee, no fund dealing charge. Vanguard comes next at £15 a year, calculated at its 0.15% charge. AJ Bell sits around £25 a year, Hargreaves Lansdown and Fidelity both land around £35 a year assuming you’re investing via a regular monthly direct debit so dealing charges are waived, and Interactive Investor’s Core plan is the most expensive of the group at £71.88 a year, because its flat fee doesn’t scale down for a smaller pot.
Two caveats worth knowing before you choose based on price alone. Trading 212 gives you access to ETFs rather than traditional funds, and its SIPP is currently in beta with no drawdown option yet, so it isn’t the platform to build a full retirement strategy around just yet. Vanguard, meanwhile, restricts you to Vanguard’s own range of funds, which is genuinely fine if that’s all you want, but limiting if you’d rather choose from a wider universe of providers. At this portfolio size, percentage based platforms almost always beat flat fee ones, and it’s worth choosing on more than price if either of those caveats matters to you.
If you are building both an ISA and SIPP with £50,000 combined
This is where the maths gets genuinely interesting, because it’s close to the point where flat fees overtake percentage fees. At £50,000 combined across an ISA and SIPP, Interactive Investor’s Core plan costs £71.88 a year, covering both accounts under a single fee. Vanguard costs £75, running neck and neck with Interactive Investor. AJ Bell comes in at £125, and Hargreaves Lansdown and Fidelity both sit at £175. This is likely close to where a lot of my readers are sitting right now, holding an ISA and starting to think seriously about consolidating pensions into a SIPP.
I know this stage well because I’ve lived just past it. My own combined balance across five accounts, a SIPP, an ISA, a trading account and two Junior ISAs, sits at around £77,000. Technically that still falls within Interactive Investor’s £100,000 Core threshold, so I could pay £71.88 a year. I’ve chosen to pay for the Plus plan at £14.99 a month instead, for the extra trade credit and family benefits that come with it, which is a personal choice rather than a necessity at my balance. The point stands either way: by the time your combined pot reaches this size, a flat fee platform is either already the cheapest option on the table, or close enough that the gap has stopped being the deciding factor.
If you hold multiple accounts with £100,000 or more
At £150,000 spread across a SIPP, an ISA and Junior ISAs, the percentage platforms start to bite properly. Vanguard costs £225 a year at this size. AJ Bell costs £375. Fidelity and Hargreaves Lansdown both cost £525. Interactive Investor’s Plus plan, required once your total portfolio crosses the £100,000 Core threshold, costs just £179.88 a year, flat, regardless of how much further your portfolio grows from here.
That’s a saving of £345.12 a year against Fidelity or Hargreaves Lansdown, £195.12 a year against AJ Bell, and £45.12 a year even against Vanguard, the cheapest percentage platform on this list. Plus also includes free Junior ISAs and family accounts, so if you’re investing on behalf of children as well as yourself, those additional accounts add nothing further to the £179.88 total. On a percentage platform, each of those accounts is typically billed separately, so the true gap in practice is often wider than the headline numbers alone suggest.
Verdict: which is best for women investors
My answer is Interactive Investor. Not for everyone, but it’s where I’d point you first.
If you’re managing more than one goal at once, your own retirement, and quite possibly something for your kids too, this is exactly where the flat fee earns its keep. One login, one monthly fee, your ISA and SIPP and Junior ISAs all included without separate charges stacking up. I’ve lived that structure for seven years, and the simplicity has mattered more than I expected it to.
That said, it won’t be right for everyone. If you’re starting out under roughly £20,000 with no immediate plans for a SIPP, the flat fee is more than you need right now, and Vanguard or Trading 212 will likely suit you better until your portfolio grows into it. And if phone based support matters more to you than a few pounds of platform fee, Hargreaves Lansdown remains a genuinely credible choice, fee changes and all.
But if you’re building a proper long term picture, an ISA and a SIPP together, maybe investing for your kids too, and expecting to grow past £50,000 over the coming years, Interactive Investor is where I’d start. It’s where I’ve stayed for seven years without once wishing I’d chosen differently.
Ready to open your stocks and shares ISA?
If what you’ve read has pointed you toward Interactive Investor, here’s how to actually get started.
This post contains my personal referral link for Interactive Investor. If you open an account using my link, you’ll receive six months fee free investing, and I’ll receive £200. This has no effect on anything else you pay, and it hasn’t influenced any of the recommendations in this guide. Everything I’ve written here is based on my own seven years of genuine experience with the platform.
Whichever platform you land on, the important thing is that you actually open one. The best stocks and shares ISA is the one you use.
FAQ
What are the best performing stocks and shares in an ISA UK?
There’s no fixed answer here, and any platform claiming otherwise should raise an eyebrow. Performance changes constantly, and past performance is never a guarantee of future returns. Rather than chasing “best performing,” most experienced investors focus on low cost, broadly diversified index funds, like a global tracker, held for the long term. Check a platform’s most traded fund lists for ideas, but always do your own research before committing.
Which UK bank has the best stocks and shares ISA UK?
Banks like Santander and Barclays do offer stocks and shares ISAs, usually with a smaller range of funds than dedicated investment platforms. If simplicity and sticking with your existing bank matters most to you, they’re worth a look. But if you want broader investment choice or lower fees, a dedicated platform such as the ones covered in this guide will typically serve you better than a high street bank.
What does Martin Lewis say about stocks and shares ISAs?
Martin Lewis’s core message is to treat investing as separate from saving. He advises only investing money you won’t need for at least five years, and only after you’ve cleared expensive debt and built an emergency fund. Done that way, he says investment returns should meaningfully outperform saving and beat inflation over time, though as with any investing, there are no guarantees attached to that outcome.
Is a stocks and shares ISA worth it in the UK?
For most people investing for the long term, yes. Any growth or income inside the ISA is protected from capital gains tax and dividend tax, and that protection compounds meaningfully over years. It’s not right for money you might need within five years, or if you haven’t cleared high interest debt first. For everyone else, it’s generally considered one of the most tax efficient ways to invest available in the UK.
Should I save in a cash ISA or invest in a stocks and shares ISA?
It depends on your timeframe. If you’ll need the money within five years, a cash ISA is the safer home, your capital isn’t at risk, though returns are modest and can be eroded by inflation. If you won’t need it for five years or more, a stocks and shares ISA has historically outperformed cash by a wide margin, in exchange for accepting that the value can fall as well as rise along the way.
Are there guarantees to protect my money in a stocks and shares ISA?
No. Unlike a cash ISA, there’s no guarantee attached to a stocks and shares ISA. The value of your investments can go down as well as up, and you could get back less than you put in. That’s the trade off for the higher long term returns investing has historically offered over cash. It’s exactly why the five year minimum timeframe and emergency fund groundwork matter before you start.
Is my money protected if the platform I invest with goes bust?
Your investments are usually held separately from the platform’s own assets, a practice known as ringfencing, so they can’t be touched even if the platform collapses. On top of that, most UK platforms are covered by the Financial Services Compensation Scheme up to £120,000 per person, per firm. This protects the platform failing, not your investments falling in value, which is a different risk entirely.
Am I better off investing my money all at once or drip feeding over several months?
Drip feeding, investing a set amount regularly rather than all in one go, is a popular way to manage risk, particularly if markets feel uncertain. Spreading purchases over time means you buy at a range of prices rather than one single point, which smooths out short term volatility. It won’t guarantee better returns than investing a lump sum, but many investors find it easier to stick with emotionally.
I am not a financial advisor and nothing in this post constitutes financial advice. All investments carry risk and the value of your investments can go down as well as up. Please do your own research and consider seeking independent financial advice before making any investment decisions.
Angelina is the founder of Investing Adventures, where she helps women build confidence with money and investing. With seven years of personal investing experience, she breaks down complex financial topics into practical, actionable advice. Her mission is simple: to help more women take the driver’s seat in their financial future.