UK Investment Fees Explained: Platform, Fund and Transaction Costs

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Every investment platform quotes its cost as a percentage, and every one of those percentages looks harmless. 0.15%. 0.25%. 0.45%. The difficulty is that the headline platform fee is only one of several charges, and they add together into a number most people never calculate. Two investors on "cheap" platforms can be paying anywhere from 0.35% to 1.5% a year once every layer is counted.

This post breaks down each layer of cost a UK investor pays, gives the typical range for each, explains where charges tend to hide, and sets out how to compare two providers on a like-for-like basis. For what those differences do to a portfolio over decades, The Real Cost of Investment Fees works through the compounding maths.

The Layers of Cost

Platform fee (also called a custody or administration fee). What the provider charges for holding your ISA, SIPP or general account and administering it. Usually 0.15% to 0.45% a year of the value held, sometimes tiered so the rate drops on larger balances, and sometimes capped in cash terms (common on SIPPs, less so on ISAs). A minority of platforms charge a flat fee instead, covered below.

Fund charge (OCF or TER). The ongoing charge of each fund you hold, deducted inside the fund before its price is published, so you never see it leave your account. A broad index tracker is typically 0.05% to 0.25%. An actively managed fund is typically 0.60% to 1.00%, occasionally more. If you hold several funds, your effective fund charge is the value-weighted average across them.

Transaction costs within the fund. The cost of the fund buying and selling its own holdings, including broker commission and the spread on what it trades. These are disclosed separately from the OCF, in the fund's costs and charges document, and are easy to miss. They might add 0.02% on a rarely-trading tracker and 0.30% or more on an active fund that turns its portfolio over frequently.

Dealing and trading fees. A per-trade charge to buy or sell. Fund dealing is often free on percentage-fee platforms; share, investment trust and ETF dealing usually costs a few pounds per trade. If you invest a fixed amount every month, a regular-investing service (often around £1.50 a trade, or free) matters more than the headline fee.

Foreign exchange fees. When you buy an overseas share or ETF priced in another currency, the platform converts your pounds and takes a margin on the rate, commonly 0.25% to 1.5% each way. Funds handle currency internally, so this mostly affects investors buying US-listed shares or ETFs directly.

Exit and transfer fees. Some platforms charge to move your investments to another provider, either a flat fee per holding or per account. These have become less common, but they still exist and are worth checking before you commit, because they raise the cost of leaving if the platform stops being competitive.

Percentage Fees vs Flat Fees

Platforms fall into two camps.

Percentage platforms charge a proportion of what you hold, so the fee scales with the portfolio. On a £20,000 ISA at 0.25%, that is £50 a year. On a £400,000 ISA at the same rate, it is £1,000 a year for administering what is, in practice, a very similar service.

Flat-fee platforms charge a set amount, for example £10 to £15 a month, regardless of balance.

For a small portfolio the percentage model is usually cheaper. For a large one the flat model can be dramatically cheaper. The crossover point depends on the specific rates, but it often sits somewhere between £100,000 and £200,000 of invested assets. Percentage platforms that cap their fee in cash terms sit in between: they behave like a percentage platform up to the cap, then like a flat-fee one above it.

What "All-In" Actually Means

Your real annual cost is the platform fee, plus the weighted fund charge, plus in-fund transaction costs, expressed as a single percentage.

• A 0.25% platform holding one 0.12% global tracker, with negligible transaction costs, is around 0.37% all-in.
• A 0.35% platform holding a 1.00% active fund with 0.20% transaction costs is around 1.55% all-in.

The gap between those two, roughly 1.2 percentage points a year, is the number that compounds. As a rough guide for UK investors, under 0.4% all-in is competitive, and much above 1% needs a clear reason.

Where Fees Hide

• In-fund transaction costs sit outside the headline OCF, so a fund advertised at "0.90%" might cost 1.10% or more in practice.
• Cash interest. Platforms hold your uninvested cash and often keep some or all of the interest it earns. On a large cash balance during a period of higher rates, the amount retained can rival the platform fee.
• FX margin on overseas holdings is a cost even though it is never labelled a fee.
• "Free" trading is usually recovered elsewhere, through a wider FX margin, cash interest retention, or payment for order flow.
• Bundled advice. Where a platform fee is quoted alongside an advice or discretionary-management charge, the platform cost and the advice cost are separate things, and worth separating on paper.

How to Compare Two Providers

The numbers that tend to matter, in order:

Total cost, not any single line. Add platform, weighted fund charge and transaction costs into one all-in percentage, and compare those.

Your portfolio against the fee structure. Run your actual balance through each platform's model: percentage, flat, tiered, or capped. The winner changes with portfolio size, so a comparison someone else ran at a different balance may not hold for yours.

How you invest. If you buy shares, investment trusts or ETFs, or invest monthly, dealing fees and any regular-investing discount can outweigh a small difference in the platform rate. If you buy funds in lump sums, they barely matter.

The cost of leaving. Check exit and transfer fees. A platform that is competitive today may not be in five years, and transfer charges determine how expensive it is to act on that.

This is a description of what the charges are and how to weigh them, not a recommendation of any provider or fund. The right choice depends on portfolio size, what you invest in, and how often you trade.

Fees Still Apply Inside an ISA or SIPP

A tax wrapper changes how your returns are taxed. It does not remove platform or fund charges. You pay the same all-in percentage on an ISA or SIPP as you would in a general account, and it is deducted in the same way, by selling units or taking it from cash. The tax treatment and the cost structure are separate questions, and both matter.

The Long-Run Effect

A fee is a drag on returns that compounds in the same way the returns themselves do. Each year's charge also removes the future growth that money would have produced, so the gap between a low-cost and a high-cost portfolio widens every year rather than staying fixed. Across a lifetime of contributions, the difference between 0.4% and 1.4% all-in commonly runs to a six-figure sum. The Real Cost of Investment Fees shows the arithmetic with an interactive comparison.

How Scenarios Helps

Scenarios lets you set an annual cost for each account or portfolio, so the fee is applied as a drag on that account's return every simulated year and accumulates into a Total Fees Paid figure across the whole plan. You can hold two versions of a plan side by side, one at 0.4% and one at 1.4%, and see the difference not as an abstract percentage but as a number of pounds, and often as months or years of retirement.

You can build a free plan and put your own fee assumption against your own contributions and timeline.