A Self-Invested Personal Pension (SIPP) is often the largest pot a UK investor will ever hold on a single platform, particularly for someone who has consolidated old workplace pensions or built up decades of contributions. Once a SIPP grows into the tens or hundreds of thousands of pounds, platform charges that felt negligible at the start can quietly become one of the biggest ongoing costs in the whole retirement plan — which is why larger pension savers often need to think about platform selection differently to someone just starting out.
Why SIPP size changes the maths
Platform charging structures for SIPPs mirror the same fixed-fee-versus-percentage-fee dynamic seen across investment platforms generally, but the stakes are higher because pension pots tend to be larger and are held for longer, often decades, without being drawn down. A 0.25% annual charge on a £30,000 SIPP is £75 a year; the same 0.25% on a £300,000 SIPP is £750 a year, for what is essentially the same amount of platform administration.
Percentage fees without a cap
Some SIPP providers charge a straight percentage with no ceiling, which means costs keep rising in direct proportion to pot size indefinitely. This structure can become expensive for a saver approaching retirement with a substantial pot.
Percentage fees with a cap
Other providers cap the percentage fee at a fixed pounds-and-pence maximum once the pot passes a certain size — for example, charging 0.25% up to £250,000 and then a flat amount above that. This structure tends to suit larger pots far better, since the cost stops rising once the cap is reached.
Fixed fees
A smaller number of providers charge a flat fee (sometimes tiered by account size) regardless of the underlying fund value. For very large pots, a flat fee can work out dramatically cheaper than an uncapped percentage fee.
A worked hypothetical example
Consider a hypothetical SIPP holder with a pot of £400,000, comparing three illustrative platform structures:
| Platform structure | Annual charge formula | Annual cost on £400,000 |
|---|---|---|
| Uncapped percentage | 0.30% of pot value | £1,200 |
| Capped percentage | 0.25% up to £250,000, then capped at £625/year | £625 |
| Flat fee | £25/month + small fund dealing fees | £300 |
In this hypothetical scenario, the uncapped percentage platform costs four times as much as the flat-fee platform for an identical set of underlying fund holdings. Over a 20-year retirement drawdown period, that difference compounds into a very large sum in cash terms — money that could otherwise have remained invested or been drawn down as income.
What larger pension savers should look at beyond the headline fee
Drawdown charges
Once a SIPP moves into drawdown, some platforms add separate charges for setting up drawdown, for each withdrawal, or for producing the paperwork associated with taking an income. These charges rarely feature prominently in headline marketing and are worth checking specifically before committing to a platform for the long term.
Fund range and dealing costs
A platform that is cheap on the headline percentage fee but charges heavily for fund dealing, or has a narrow fund range that doesn't include the type of fund an investor wants (for example, a broad global tracker or a multi-asset fund), may not actually be the cheapest or most suitable overall choice.
Consolidation costs
Larger SIPPs are often built by transferring in several old pensions. Some platforms offer to cover exit fees charged by a previous provider, up to a certain amount, as an incentive to transfer — this is worth factoring into the overall cost comparison, though it should not be the only reason for choosing a platform.
Additional services
Some platforms bundle in research tools, model portfolios, or access to a wider range of investment trusts and offshore funds, which may or may not be relevant depending on how actively an investor wants to manage the underlying selections.
Percentage caps and why they matter specifically to fund investors
Fee caps are frequently applied only to fund holdings, not to shares, investment trusts, or ETFs held on the same platform. An investor who holds their SIPP mostly or entirely in open-ended funds may benefit from a fee cap that a share-only investor on the same platform never reaches. This distinction is explored in more depth in the companion article on how platform fee caps work, but it is particularly relevant for larger pension pots, where the fund/share split can materially change the total cost.
Consolidating multiple pensions into one larger SIPP
Many larger SIPPs are not built from a single employer's pension but assembled over a career from several old workplace schemes, each potentially carrying its own charging structure, fund range, and exit terms. Bringing these together onto a single platform can simplify administration and, in many cases, reduce total cost — but it needs to be weighed carefully rather than assumed to always be beneficial.
Reasons consolidation often helps larger pots
- A single, larger pot is more likely to benefit from a fee cap or a favourable tiered rate than several smaller pots spread across different providers, each too small individually to reach a lower tier.
- Older pensions, particularly older-style personal pensions from the 1990s and 2000s, sometimes carry legacy charges — high annual management charges bundled into the fund itself, or exit penalties — that are simply not competitive by current standards.
- Managing a single platform's paperwork, beneficiary nominations, and investment choices is materially simpler than juggling several separate accounts, particularly for a saver approaching retirement who needs a clear view of their total position.
Reasons to check carefully before consolidating
- Some older pensions include valuable guarantees — a guaranteed annuity rate, or safeguarded benefits — that would be permanently lost on transfer, and by law often require regulated financial advice before transferring if the pension has significant safeguarded benefits (broadly, those valued over £30,000).
- Some legacy schemes include life cover or other benefits bundled into the pension that a straightforward SIPP transfer would not replicate.
- Exit penalties on the old scheme need to be weighed against the ongoing saving from consolidating, exactly as discussed in the general article on hidden platform costs.
Investment pacing and cash management for larger pots
A larger SIPP also raises practical questions around how contributions and withdrawals are timed. Someone making a large one-off contribution using carried-forward annual allowance, for example, may want to consider whether to invest the whole sum immediately or phase it in gradually, and different platforms vary in how easily and cheaply they support regular, automated investment of large cash balances into chosen funds. Similarly, someone approaching drawdown may want to hold a portion of the SIPP in lower-risk assets or cash to fund near-term withdrawals, and it's worth checking whether a platform pays any interest on uninvested cash balances, since this can vary noticeably between providers and becomes more financially relevant as balance sizes grow.
Comparing customer service and support at scale
For a smaller, more straightforward pension, most platforms' customer service is broadly interchangeable. For a larger, more complex SIPP — perhaps involving multiple consolidations, drawdown planning, or beneficiary nominations across a blended family — the quality of a platform's support, the clarity of its drawdown paperwork, and the availability of telephone or in-person guidance (as distinct from regulated advice) can matter more in practice than a small difference in the headline percentage fee. This is a genuinely subjective factor, but larger pension holders may reasonably give it more weight than someone with a modest, simple pot.
Practical steps before choosing or switching a SIPP platform
- Calculate the current annual cost on the existing platform, including the underlying fund OCFs, not just the platform fee.
- Project the pot forward to a realistic retirement value and re-run the calculation, since the cheapest platform today may not be cheapest once the pot has grown.
- Check whether a percentage fee is capped, and at what pot size the cap applies.
- Ask what charges apply once the SIPP enters drawdown, not just during the accumulation phase.
- Weigh any transfer-in incentives against the ongoing annual saving, since a one-off bonus is less valuable than a lower fee sustained over 20 or 30 years.
Comparing charge disclosure quality across providers
Not all SIPP providers present their charges with equal clarity. Some publish a single, easy-to-follow document showing exactly what a saver would pay at various pot sizes and in various scenarios (accumulation, drawdown, transfer-out); others spread charges across several documents, or bury drawdown-specific fees in a separate terms booklet only provided once an account is opened. For a larger, longer-term SIPP, this difference in disclosure quality is itself worth weighing as part of the decision — a provider that is transparent about all its charges upfront makes it much easier to plan accurately for the decades ahead, while one that is vague or scattered increases the risk of an unwelcome surprise later, for instance on first entering drawdown.
The pension annual allowance and why platform costs compound alongside contributions
For 2025/26 the pension annual allowance is £60,000 (or 100% of earnings if lower), with unused allowance from the previous three tax years potentially available to carry forward. Higher earners making large annual contributions, or those using carry-forward to make a substantial one-off contribution, can see their SIPP grow quickly — which means the platform cost structure chosen today may need to comfortably suit a considerably larger pot within just a few years. Always check current HMRC allowance figures, as these are reviewed and can change.
Key takeaways
- Platform charges that seem small on a modest SIPP can become one of the largest ongoing costs once a pension pot grows into six figures.
- Uncapped percentage fees can become very expensive for larger pots; capped percentage fees and flat fees tend to scale much better.
- Drawdown-specific charges, dealing costs, and fund range all matter alongside the headline percentage or flat fee.
- Fee caps that apply specifically to fund holdings can make a real difference for investors who hold mostly open-ended funds rather than shares.
- It is worth recalculating platform costs as a pot grows, and before and after moving into drawdown, rather than assuming an early choice remains the cheapest option indefinitely.