Country scope: United Kingdom
Flat vs percentage platform fees: where is the intersection?
For simple uncapped charges, divide the flat annual fee by the percentage rate written as a decimal. A £120 annual fee and a 0.25% annual fee intersect at £48,000, but real platform schedules can include caps, tiers, wrapper charges, dealing fees and exclusions, so the intersection is not a universal break-even point.
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Why this matters when choosing a broker
Fee structure changes how a platform charge responds to portfolio value. A flat charge stays fixed for the stated period; a simple percentage charge changes with the applicable asset value.
A correct intersection helps compare two defined rules, but it does not establish the cheaper complete platform or a suitable provider. Other charges and capabilities must be held constant.
Flat fee
A flat fee is a stated money amount for a stated period or service. Confirm whether it is monthly or annual, whether separate wrappers are charged separately, and whether the price includes any dealing credits or subscription features.
Percentage fee
A percentage platform fee applies a rate to a defined base, often eligible assets or portfolio value. Confirm which assets are included, when the value is measured, and whether tiers, minimums or caps change the arithmetic.
Real schedules can change the intersection
The FCA has documented both flat and percentage platform structures and emphasizes comparing total charges with a breakdown. A single headline platform rate is not enough when other account, dealing, FX, fund or transfer costs differ.
- A cap can stop a percentage charge from continuing to rise.
- Marginal tiers apply different rates to different bands; they are not the same as applying one rate to the whole balance.
- Wrapper-specific charges can create separate calculations for GIA, ISA and SIPP.
- Dealing and product costs can change the complete scenario without changing the platform-fee intersection.
Worked comparison
Common mistakes and misinterpretations
- Dividing by 0.25 instead of converting 0.25% to 0.0025.
- Calling the intersection a universal winner or suitability threshold.
- Ignoring caps, tiers, minimums or wrapper-specific charges.
- Comparing only platform charges when dealing, FX or product charges differ.
- Using an end-of-year balance when the provider uses a different valuation method.
How to apply this
Open a functional destination with the relevant country or account filter applied. Recheck current official terms before acting.
Key takeaways
- For simple rules, intersection equals flat annual fee divided by the decimal percentage rate.
- The calculation is valid only for the stated fee bases and assumptions.
- Model caps, tiers and other charges before comparing provider-specific totals.
- Cost does not replace eligibility, investment access or other material limitations.
Official and authoritative sources
These pages were checked for the claims used in this guide. Follow the descriptive link to verify the current source.
- Investment platform costs and charges review: FCAFinancial Conduct Authority · checked
- Investment Platforms Market Study: FCAFinancial Conduct Authority · checked