What are investment platform and fund fees actually costing you?
More than the headline figure, because charges come in several layers that are disclosed separately — and the cumulative effect over decades is far larger than the annual percentages suggest.
The layers:
Platform fee, charged by the service holding your investments — either a percentage of the value or a flat annual fee. Which is cheaper depends entirely on portfolio size, and the crossover point is the single most valuable calculation an investor can do: percentage fees are cheaper on small portfolios, flat fees dramatically cheaper on large ones.
Fund ongoing charges (OCF), deducted inside the fund itself. This does not appear on any statement as a payment — it is reflected in the fund's price — which is precisely why it is easy to ignore.
Transaction costs inside the fund, from its own trading, disclosed separately and additional to the OCF.
Dealing charges when you buy or sell.
Foreign exchange charges on overseas holdings, frequently the least visible and sometimes the largest single cost for international investing.
Exit or transfer fees, now restricted but not gone.
Adviser fees, where an adviser is involved, on top of everything above.
Why it matters so much more than it looks. Fees compound against you exactly as returns compound for you. The difference between total costs of 0.3% and 1.3% a year, sustained over a working life, commonly consumes a very substantial fraction of the final pot — a figure that surprises people every time it is calculated, because the annual difference sounds trivial.
What to actually do:
Add up all the layers, not just the platform fee.
Check the crossover between percentage and flat-fee platforms for your portfolio size, and recheck as it grows.
Compare index funds on total cost, since they hold near-identical assets and cost is one of the few reliable predictors of relative return.
Watch currency conversion if investing internationally.
Beware cost-driven churn. Switching platforms has its own costs and time out of the market.
General information, not financial advice.