Capped-fee pensions — are they worth it for large pots?
Once your pot crosses the cap threshold, every pound of additional growth is effectively managed for free. Here's the crossover point, the trade-offs, and how to compare capped structures against uncapped percentage fees.
- ▸At 0.45% with a £375 annual cap, the cap kicks in at £83,333. Above that pot size, the effective fee rate falls with every pound of growth — and at £500,000, you're paying an effective rate of just 0.075%.
- ▸True flat-fee platforms (e.g. Interactive Investor at £5.99/month = £71.88/year) are even cheaper for large pots but more expensive than percentage-fee providers for pots under roughly £20,000–30,000.
- ▸The saving from a capped fee versus an uncapped 0.45% fee on a £300,000 pot is £975/year — compounding to over £15,000 in 20 years at 5% growth.
- ▸The main trade-off is that capped/flat-fee providers sometimes offer narrower fund ranges than full-service percentage-fee platforms, though passive investors rarely need more than a handful of funds.
How capped and flat fees work
Most UK pension platforms charge a percentage of your pot as their annual platform fee. This scales linearly: 0.45% on £50,000 is £225; on £500,000 it's £2,250. The fee keeps growing as the pot grows.
Capped fees modify this structure. The platform charges a percentage up to a maximum pound amount per year. Once your pot reaches the cap threshold, the annual charge stays fixed regardless of how large the pot grows. Vanguard's UK SIPP charges 0.15% per year, capped at £375 — so on a £1 million pot, you're paying £375/year rather than £1,500.
Flat fees are an extreme version of this: a fixed monthly or annual charge with no percentage component at all. Interactive Investor's SIPP charges £5.99/month (£71.88/year). Whether you hold £50,000 or £1,000,000, the platform charge is the same.
Both structures benefit large pots significantly. The question for any given saver is: at what pot size does the structure start to work in your favour?
The crossover point where flat beats percentage
The crossover point is simple to calculate. For a capped fee, it's the pot size at which the percentage fee equals the cap amount:
Cap ÷ percentage rate = crossover pot size
Examples at common cap/rate combinations in the UK market:
| Cap | Rate | Crossover pot |
|---|---|---|
| £375 | 0.45% | £83,333 |
| £375 | 0.15% (Vanguard) | £250,000 |
| £500 | 0.45% | £111,111 |
| £71.88/yr | Flat (II) | Crossover vs 0.45%: £15,973 |
The Vanguard example is instructive: the cap of £375 on a 0.15% rate means the crossover isn't until £250,000 — a large pot. But below £250,000, 0.15% is still cheaper than most competitors' uncapped rates, so Vanguard tends to win across most pot sizes.
For a provider charging 0.45% with a £375 cap, the crossover against an uncapped 0.45% provider is obviously the same pot (there's no advantage until you compare against a different capped or flat provider). The comparison that matters is between this capped 0.45% provider and an uncapped provider at any rate — or between two providers at different structures.
Compare: 0.45% uncapped versus 0.15% capped at £375:
- At £50,000: uncapped = £225, capped = £75 — capped wins by £150/year
- At £83,333: uncapped = £375, capped = £125 — capped wins by £250/year
- At £250,000: uncapped = £1,125, capped = £375 — capped wins by £750/year
- At £500,000: uncapped = £2,250, capped = £375 — capped wins by £1,875/year
The pension fee calculator models any combination of structures against your specific pot and time horizon.
What this means for growing pots
The economic benefit of a capped fee increases as your pot grows — but it also increases retrospectively as your pot has grown in the past. This means the longer you've been on an uncapped percentage-fee platform, the more you've been overpaying relative to what a capped provider would have charged.
A worked example: suppose you started with £50,000 15 years ago on an uncapped 0.45% platform. Your pot has grown at 5% per year to roughly £104,000 today. Over that 15 years, you paid cumulative platform fees of approximately £9,700. On a 0.15%/£375-cap structure, you'd have paid approximately £3,600 — a difference of over £6,000. And the compounding effect of that £6,000 retained in the pot is another £3,000–4,000 in foregone growth.
Looking forward from a £104,000 starting point, switching to the capped structure saves roughly £90/year initially, growing to over £1,500/year by the time the pot reaches £500,000 — assuming continued growth. Over 20 years, the total saving compounds to a significant sum.
The providers page at /providers compares current UK SIPP and personal pension providers by structure, allowing you to filter by pot size to find the cheapest option for your specific situation.
The trade-off: narrower fund range vs lower cost
Flat-fee and capped-fee providers generally offer either:
-
A proprietary fund range only — Vanguard's SIPP only offers Vanguard funds. If your preferred investment is a Vanguard global tracker, this isn't a constraint. If you want to hold individual stocks, sector ETFs, or third-party active funds, it is.
-
A full fund platform with trade-based pricing — Interactive Investor charges per trade (£5.99/trade after the first per month). For a buy-and-hold investor making a few trades per year, this is cheap. For an active trader or someone building a complex multi-fund portfolio, it can add up.
The practical implication for the majority of pension savers: if your investment strategy is a single global index tracker or a small number of passive funds — which the evidence strongly supports as appropriate for most long-term pension savers — the narrower fund range at capped/flat-fee providers is rarely a meaningful constraint.
The fee saving at large pot sizes is substantial. A saver with £300,000 in an uncapped 0.45% provider and 20 years to retirement who switches to a capped 0.15%/£375 provider saves approximately £975/year immediately, rising as the pot grows. Over 20 years, that cumulative saving, retained in the pot and compounding, adds over £30,000 to the final pot — from a decision that takes an afternoon to execute. Our guide to pension fees covers the full picture on when switching makes financial sense.
- ▸At a 0.45% annual fee with a £375 annual cap, the cap kicks in at a pot size of £83,333. Above that pot size, every additional pound of growth is held at no additional platform cost. [Pension Bible calculation]
- ▸Vanguard's UK SIPP charges 0.15% per year capped at £375 per year — making it free above £250,000 in effective additional cost as the pot grows beyond the cap. [Vanguard]
- ▸Interactive Investor charges a flat £5.99 per month for its SIPP — an annual cost of £71.88, regardless of pot size. At £100,000, this equates to an effective rate of 0.072%. [Interactive Investor]
This is factual information, not financial advice. If you're unsure what's right for your situation, speak to an FCA-regulated financial adviser.