Best SIPP Providers in the UK: Self-Invested Pensions Compared

There is no single best SIPP in the UK, because the right self-invested personal pension depends almost entirely on your pot size and how you invest. The one rule that decides most of it is simple: percentage-based platforms are cheaper for smaller pots, and flat-fee platforms are cheaper for larger ones. Get that match right and you can save thousands over a couple of decades. This guide compares the main providers by fee model, so you can find the cheapest home for your pension rather than the most advertised one. Fees quoted are as of 2026; always confirm the current charges before you open or transfer.

The one decision that matters: flat fee vs percentage

Every SIPP charges a platform (admin) fee for holding your money, and this is where the big differences live:

• Percentage fees (a set % of your pot per year) are cheapest when your pot is small, because a small percentage of a small number is tiny. They grow as your pot grows.
• Flat fees (a fixed £ per month regardless of pot size) look expensive on a small pot but become far cheaper once your pot is large, because the fee stops rising.

Somewhere between roughly £50,000 and £150,000, depending on the providers, a flat-fee platform overtakes a percentage one. On a very large pot the gap is enormous: on a £1 million pension, a flat-fee platform can cost a couple of hundred pounds a year while a percentage platform can cost thousands.

On top of the platform fee, watch dealing charges (per trade for shares or ETFs) and the fund’s own OCF, which is separate from the platform and explained in our guide to fund fees and the OCF.

The main UK SIPP providers compared

interactive investor (ii): best for larger pots

ii uses a flat monthly fee rather than a percentage, which makes it the standout for larger pensions. Once your pot is into six figures, a fixed monthly charge dominates every percentage-based rival, and the saving compounds every year your pot grows. The trade-off is that the flat fee feels heavy on a small starting pot, so ii tends to suit those who already have, or are building towards, a substantial pension. It offers a very broad range of funds, shares and ETFs.

AJ Bell: strong all-rounder

AJ Bell charges a percentage platform fee that is capped, with a separate lower cap for shares and ETFs, plus a modest per-trade dealing charge. The cap means it stays reasonable as your pot grows, and the investment range is wide (thousands of funds plus shares, ETFs and investment trusts). It is a sensible default for people who want choice without committing to a flat fee.

Hargreaves Lansdown: most features, higher fund fee

HL is the largest UK platform, with the deepest research, tools and customer service. It charges a tiered percentage fee on funds that steps down as your pot grows, with lower or no charges on very large holdings, and a cap on the share/ETF portion. You pay for the polish: on funds it is one of the pricier options for a mid-sized pot. Best if you value the service and tools and hold mostly shares, ETFs or a large pot.

Vanguard: cheapest for simple index investing

Vanguard’s SIPP has a low percentage platform fee with an annual cap, but you can only invest in Vanguard’s own funds and ETFs. For a passive investor who just wants a global index fund or a LifeStrategy portfolio, that limitation is not a problem and the cost is very low. If you want shares or other providers’ funds, look elsewhere. See our Vanguard UK review for the detail.

Others worth knowing

Fidelity, Bestinvest and newer low-cost apps also offer SIPPs. App-based providers can be cheap and simple but sometimes offer a narrower range or fewer retirement (drawdown) options, so check they support how you plan to eventually take an income.

Which SIPP is best for you

• Small pot, just starting: a capped-percentage platform like AJ Bell, or Vanguard if you only want index funds. The percentage keeps costs tiny while the pot is small.
• Passive index investor: Vanguard for its own funds, or a low-cost broad platform if you want wider choice.
• Large pot (roughly £100k+): a flat-fee platform like interactive investor, where the fixed charge saves the most as the pot grows.
• Want the most tools and service: Hargreaves Lansdown, accepting a higher fund fee.

The single biggest mistake is leaving a large pot on a percentage platform for years without checking whether a flat fee would now be cheaper. Re-run the sums whenever your pot crosses a big milestone.

Before you open or transfer

• Check exit and transfer fees, both at your old provider and the new one.
• Confirm drawdown options and charges, because that is how you will eventually take the money.
• Do not transfer a pension with safeguarded benefits (like a defined-benefit or final-salary scheme, or a guaranteed annuity rate) without regulated advice. The government-backed MoneyHelper guide to SIPPs explains the risks in plain terms.

Ready to act? Our guides on how to open a SIPP in the UK and UK pensions explained walk through the mechanics, and best investment platforms in the UK compares the same providers for ISAs and general accounts.

Frequently asked questions

What is the best SIPP provider in the UK? There is no single best one. Percentage-fee platforms like AJ Bell or Vanguard are cheapest for smaller pots, while flat-fee platforms like interactive investor are cheapest for larger pots. Match the fee model to your pot size and how you invest.

Is a flat-fee or percentage SIPP cheaper? Percentage fees are cheaper on small pots; flat fees are cheaper on large ones. The crossover is usually somewhere between about £50,000 and £150,000, so a growing pot can eventually be better off switching to a flat-fee platform.

What is the cheapest SIPP for a large pension pot? A flat-fee platform, such as interactive investor, because the charge stops rising as the pot grows. On a very large pot this can save thousands a year versus a percentage-based platform.

What is the cheapest SIPP for index funds? Vanguard is very cheap if you are happy to hold only its own funds and ETFs. If you want a wider index-fund range, a low-cost broad platform with a capped percentage fee is the alternative.

Can I transfer my old pensions into a SIPP? Usually yes, and combining old pots into one SIPP can cut fees and admin. But never transfer a defined-benefit or other safeguarded pension without regulated financial advice, as you could lose valuable guarantees.

Do SIPP fees include the fund charges? No. The platform fee is separate from each fund’s own ongoing charge (the OCF) and any dealing charges. To compare true cost, add all three together for your likely holdings.