We compare the total annual cost of investing across the UK’s most popular ISA platforms using £10k, £50k and £100k portfolios. In practice, the “cheapest” platform isn’t always obvious — it depends heavily on what you invest in, how often you invest, and how large your portfolio becomes over time.

Investment fees may look small — 0.25%, 0.35%, even 0.50% — but over decades they can significantly reduce long-term portfolio growth. This is one of the most commonly overlooked aspects of investing — especially for beginners who focus on performance but underestimate the impact of fees.

Disclosure: Some links in this article may be affiliate links. This means we may receive a small commission if you open an account through these links, at no additional cost to you. This helps support the site and keeps our guides free to read.

Summary: Based on our modelling, a few clear patterns emerge. Trading 212, InvestEngine and IG are typically the cheapest platforms for ETF investors, while AJ Bell is often the lowest-cost option for traditional funds at smaller portfolio sizes.

Jump to:

• Cheapest ISA platforms for funds
• Cheapest ISA platforms for ETFs
• Which platform is cheapest overall

Which is the cheapest Stocks & Shares ISA in the UK?

The cheapest Stocks & Shares ISA platforms in the UK depend on what you invest in.

For ETF investors, Trading 212, InvestEngine and IG are typically the lowest-cost platforms because they charge no platform fee.

For fund investors (OEICs), AJ Bell is usually the cheapest platform for smaller portfolios, while flat-fee providers such as Interactive Investor become competitive as portfolios grow.

The tables below compare the total annual cost of investing across the UK’s major ISA providers at £10k, £50k and £100k portfolio sizes.

How this comparison works

We model:

• Platform fees (percentage, flat or tiered)
• Ongoing fund costs (OCF)
• Regular investing dealing charges (12 trades per year)

We compare two scenarios:

Funds (OEICs) – based on a 0.23% OCF (Vanguard FTSE Global All Cap)
ETFs – based on a 0.22% OCF (Vanguard FTSE All-World ETF)

We’ve kept the assumptions simple so that comparisons are consistent, but actual costs can vary slightly depending on how you invest in practice.

All figures shown are annual costs.

Foreign exchange charges are excluded from the base case unless noted.

Assumptions used

• 12 regular investments per year
• Portfolio sizes: £10,000 / £50,000 / £100,000
• Funds OCF assumed: 0.23%
• ETF OCF assumed: 0.22%
• FX costs excluded unless stated
• Fees taken from published provider fee schedules

Annual Cost Comparison – OEIC (Fund) Investing

The table below compares the annual cost of investing in traditional funds (OEICs) across major UK Stocks & Shares ISA platforms.

Platform	£10,000	£50,000	£100,000	Notes
AJ Bell	£48 Cheapest	£240	£480	0.25% platform fee. £1.50 regular fund trades included in model.
Fidelity	£58	£290	£580	0.35% platform fee. £90 annual minimum under £25k.
Hargreaves Lansdown	£58	£290	£580	0.45% platform fee (new fee structure from Mar 2026). Fund dealing free via regular investing.
IG	N/A	N/A	N/A	ETF-only provider. No traditional OEIC funds.
Interactive Investor	£95	£187 Cheapest	£302 Cheapest	Flat fee (£5.99/month). Regular fund investing free.
InvestEngine	N/A	N/A	N/A	ETF-only platform. No traditional OEIC funds.
Trading 212	N/A	N/A	N/A	ETF-only platform. No traditional OEIC funds.
Vanguard	£71	£190	£380	0.15% platform fee (£4/month under £32k; £375 annual cap).

IG, InvestEngine and Trading 212 are ETF-only platforms and do not offer traditional OEIC funds. Costs shown reflect modelling assumptions for comparison purposes only.
Fee data last updated: March 2026.
Fees sourced from publicly available platform schedules (for example, Vanguard’s published fee schedule).

Takeaway: At £10,000, percentage-based platforms such as AJ Bell are typically cheapest, while at £50,000–£100,000 flat-fee platforms can become more cost-effective.

In reality, most investors won’t notice small fee differences at lower portfolio sizes — but as your investments grow, these differences become much more meaningful.

Key Observations – OEIC Investors

At smaller portfolio sizes (£10,000), percentage-based platform fees tend to be the most competitive.
Platforms such as AJ Bell, Fidelity and Hargreaves Lansdown remain relatively cost-efficient at lower balances because the percentage fee is applied to a smaller portfolio value.

As portfolios grow, platform fee structures start to matter more.
At £50,000 and £100,000 portfolios, the difference between platform charging models becomes more visible. Percentage-based platforms continue to scale with portfolio size, meaning costs increase as investments grow.

Flat-fee platforms can become more competitive at larger balances.
Platforms such as Interactive Investor, which charge a fixed subscription fee rather than a percentage of assets, become relatively more attractive as portfolio size increases.

ETF-only platforms appear cheapest in the table but are not comparable for fund investors.
Platforms such as Trading 212, InvestEngine and IG do not currently offer traditional OEIC mutual funds. Their costs are therefore shown for completeness but they are only suitable for ETF investors.

For investors using traditional mutual funds, percentage-based platforms remain competitive at smaller balances, while flat-fee models become more attractive as portfolios grow.

ETF vs OEIC: What’s the Difference?

Traditional investment funds in the UK are typically structured as OEICs (Open-Ended Investment Companies), while ETFs (Exchange-Traded Funds) trade on stock exchanges like individual shares.

Both can track the same index, but they differ in how they are bought, sold and priced:

• OEICs are priced once per day and can be purchased directly from fund platforms.
• ETFs trade throughout the day on the stock market and may involve dealing charges.

ETFs often have slightly lower ongoing costs, but the best option depends on how frequently you invest and the size of your portfolio.

For a full breakdown, see our guide: ETF vs OEIC – What’s the Difference?

In recent years, many platforms have introduced fractional ETF investing, making ETFs easier to invest in regularly.

Stocks & Shares ISAs are regulated under rules set by HMRC, including annual contribution limits and tax treatment (see official HMRC guidance).

Annual Cost Comparison – ETF Investing

Exchange-traded funds (ETFs) are increasingly popular due to their typically lower ongoing charges and the availability of low-cost ETF-focused platforms. The table below compares the total annual cost of investing in ETFs across the same three portfolio sizes, assuming regular monthly investing.

For many investors, ETFs have become the default option – largely because of their lower costs and increasing availability on low-fee platforms.

Unlike the OEIC comparison above, the table below compares the annual cost of investing in ETFs using regular monthly investing.

Platform	£10,000	£50,000	£100,000	Notes
AJ Bell	£89	£194	£304	0.25% custody fee (shares account). £3.50 regular ETF trades.
Fidelity	£75	£218	£328	£90 annual minimum under £25k. £1.50 regular ETF trades.
Hargreaves Lansdown	£57	£260	£370	0.45% custody fee capped at £150/year for ETFs.
IG	£22 Cheapest	£110 Cheapest	£220 Cheapest	ETF-only provider. No platform fee.
Interactive Investor	£142	£230	£340	Flat fee (£5.99/month). £3.99 per ETF trade.
InvestEngine	£22 Cheapest	£110 Cheapest	£220 Cheapest	ETF-only. No platform or dealing fees (managed option not modelled).
Trading 212	£22 Cheapest	£110 Cheapest	£220 Cheapest	ETF-only. No platform fee (FX fees not modelled).
Vanguard	£70	£185	£370	0.15% platform fee (£4/month under £32k; £375 cap). No ETF dealing charge.

Fee data last updated: March 2026.
Fees sourced from publicly available platform schedules (for example, Vanguard’s published fee schedule).

Takeaway: ETF-only platforms such as Trading 212, InvestEngine and IG are typically cheapest due to zero platform fees, but may be less suitable if you need access to traditional funds.

Key Observations – ETF Investors

ETF-focused platforms dominate the cost rankings.
Platforms such as Trading 212, InvestEngine and IG consistently appear as the lowest-cost options across all portfolio sizes in this comparison. This is largely because these platforms charge no platform fee, meaning investors only pay the underlying ETF cost.

Traditional platforms remain competitive at larger balances.
Platforms such as Vanguard, AJ Bell and Fidelity charge platform fees, but these can still be reasonable depending on the portfolio size and trading activity. For investors who want access to a wider range of investments or additional account types, these platforms may still be attractive.

Trading costs matter when investing regularly.
Platforms that charge dealing fees for ETF purchases can become more expensive when investing monthly. For example, a £1.50 trade executed 12 times per year adds £18 in annual costs.

ETF-only platforms have limitations.
Low-cost providers such as Trading 212 and InvestEngine do not offer traditional OEIC funds and may have fewer research tools or product options compared with full-service platforms.

For investors focused purely on ETFs, zero-platform-fee providers can significantly reduce long-term investment costs.

Which ISA Platform Is Cheapest?

There isn’t a single platform that is cheapest in every scenario – which is why comparing based on your own portfolio size and investment type is important.

While platform fees vary depending on portfolio size and investment type, the comparison above highlights a few clear patterns.

Cheapest for Smaller Portfolios (£10,000)

For investors starting with smaller balances, percentage-based platforms remain competitive because the platform fee is applied to a relatively small portfolio value.

However, ETF-focused providers such as Trading 212 and InvestEngine appear cheapest overall due to their zero-platform-fee model, assuming you are comfortable investing exclusively in ETFs.

---

Cheapest for Medium Portfolios (£50,000)

At mid-sized portfolios, platform fee structures become more important. Percentage-based platforms begin to look more expensive as portfolio values increase, while flat-fee platforms or zero-fee ETF platforms can offer meaningful cost advantages.

For investors using traditional mutual funds (OEICs), the lowest cost platform may still be one of the mainstream providers depending on the exact fee structure and dealing charges.

---

Cheapest for Larger Portfolios (£100,000)

At higher portfolio values, platform fee caps and flat-fee models start to dominate. Platforms that charge a fixed subscription or apply fee caps can become significantly cheaper than percentage-based alternatives.

ETF-only platforms continue to show the lowest costs in the ETF comparison, but investors should consider whether their investment strategy requires access to OEIC funds, research tools, or a wider product range.

---

The Key Takeaway

The cheapest ISA platform depends on three main factors:

• The size of your portfolio
• Whether you invest in funds (OEICs) or ETFs
• How frequently you trade

For investors focused purely on ETFs and minimising fees, zero-platform-fee providers can offer the lowest ongoing costs. For fund investors or those seeking broader investment features, traditional platforms may still represent good value.

Who Each Platform Suits

While cost is important, most investors don’t choose a platform based on fees alone. Ease of use, investment choice and long-term flexibility can matter just as much.

Each platform has a slightly different fee structure and investment offering. The best choice will depend on your portfolio size, investment style, and whether you prefer funds or ETFs.

If you’re just getting started, you may prefer a simpler platform – see our beginner ISA guide.

Vanguard Investor

Best for: Simple long-term investing in Vanguard funds and ETFs.

Vanguard offers a straightforward platform focused on its own range of low-cost funds and ETFs. The platform fee is relatively low and capped annually, making it a popular option for long-term passive investors who are comfortable investing primarily in Vanguard products.

---

Hargreaves Lansdown

Best for: Investors who value research tools and a broad investment range.

Hargreaves Lansdown is one of the UK’s most established investment platforms and offers access to a wide selection of funds, shares and ETFs. While its percentage-based platform fee can become more expensive for larger portfolios, the platform provides strong research tools and a well-developed mobile and web experience.

---

AJ Bell

Best for: Investors seeking a balance between platform features and cost.

AJ Bell offers a competitive fee structure and access to a broad range of investments, including funds, shares and ETFs. Its platform fees sit between lower-cost ETF providers and more premium platforms, making it a balanced option for many investors.

---

Fidelity

Best for: Long-term investors who prefer funds and regular investing.

Fidelity’s platform supports a wide range of mutual funds and ETFs, with no dealing charge for fund purchases. Its percentage-based fee structure can be competitive at smaller portfolio sizes, particularly for investors who prefer regular contributions.

---

Interactive Investor

Best for: Larger portfolios that benefit from a flat monthly fee.

Interactive Investor charges a flat subscription fee rather than a percentage of assets. This structure becomes increasingly attractive for larger portfolios where percentage-based fees would otherwise scale with portfolio size.

---

Trading 212

Best for: Low-cost ETF investors who want a simple mobile-first platform.

Trading 212 offers commission-free investing in shares and ETFs and does not charge a platform fee. However, it does not support traditional mutual funds (OEICs), meaning it is primarily suitable for ETF-based investment strategies.

---

InvestEngine

Best for: Investors building ETF portfolios with minimal platform costs.

InvestEngine focuses on ETF investing and does not charge a platform fee for its DIY portfolios. Like Trading 212, it does not currently support traditional OEIC funds, so it is best suited to investors comfortable using ETFs exclusively.

---

IG

Best for: Investors who want ETF investing alongside a broader trading platform.

IG offers a stocks and shares ISA with access to shares and ETFs. While it is primarily known as a trading platform, its ISA offering can be competitive for ETF investors, although it does not currently support traditional OEIC mutual funds.

---

Other Factors to Consider When Choosing an ISA Platform

While platform fees can have a meaningful impact on long-term investment returns, they are not the only factor worth considering when selecting a Stocks & Shares ISA provider.

Investment Range

Some platforms specialise in ETFs, while others offer a wider range of investments including mutual funds, individual shares, investment trusts and bonds. Investors who prefer traditional mutual funds may need to choose a platform that supports OEICs, whereas ETF-focused investors may have more options.

Platform Experience

The usability of a platform’s website and mobile app can make a significant difference to the investing experience. Some platforms offer advanced research tools, portfolio analytics and educational resources, while others focus on a simpler, lower-cost interface.

Additional Accounts

Many investors eventually open additional accounts alongside their ISA. Some providers offer a broader range of products such as Self-Invested Personal Pensions (SIPPs), Junior ISAs or general investment accounts, which can make it easier to manage multiple investments within the same platform.

Customer Support

Customer service can also be an important consideration, particularly for new investors. Established platforms often provide extensive help centres and telephone support, while lower-cost platforms may rely more heavily on digital support channels.

---

Final Thoughts

Platform fees may appear small, but over time they can make a meaningful difference – particularly as your portfolio grows.

For most investors, the goal isn’t to find the absolute cheapest platform, but one that keeps costs low while still being easy to use and suitable for long-term investing.

This comparison shows that the cheapest platform depends largely on how you invest — whether you prefer ETFs or mutual funds, how frequently you invest, and the size of your portfolio.

ETF-focused platforms can offer extremely low ongoing costs, while traditional investment platforms may provide a wider investment range and additional features that some investors value.

Ultimately, the best ISA platform is the one that balances cost, investment choice and usability in a way that supports your long-term investment strategy.

If you’re looking beyond cost alone, see our guide to the best Stocks & Shares ISAs in the UK.

FAQs