Investment Fees Explained: Flat Fees vs Percentage Fees

Investment platforms charge in two fundamentally different ways: a flat fee that stays the same whatever you hold, or a percentage fee that scales with your balance. Which one costs you less depends on a number only you know — how much you hold, and how that changes over time. This guide works through the arithmetic with examples, then points you to calculators that run it on your own figures.

What You Are Actually Choosing Between

“Investment app” covers three different products, and picking the wrong category costs more than picking the wrong brand within a category.

• A self-directed brokerage. You choose what to buy. The app executes and holds it. Maximum control, and all the decisions are yours — including the ones you make badly in a falling market.
• An automated investing service. You answer questions, the service builds and maintains a portfolio to a rule. Fewer decisions, a management fee, and the specific advantage of rebalancing happening whether or not you feel like it. Covered in full in our guide to robo-advisors.
• A round-up or micro-investing app. Small amounts move automatically, usually into a preset portfolio. Its real product is the habit, not the returns.

A fourth thing gets shelved alongside them and is not an investment app at all: a charting tool shows you price data but holds nothing and executes nothing. You still need a broker.

Why a Flat Monthly Fee Behaves So Differently from a Percentage

This is the single most useful piece of arithmetic on this page, and it is the one most consistently left out of app comparisons.

A percentage fee scales with your balance: 0.25% a year is 0.25% whether you hold a little or a lot. A flat monthly subscription does not scale — it is a fixed number of currency units regardless of balance, which means its percentage cost falls as your balance grows and rises sharply as your balance shrinks.

Work it through. A flat fee of $3 a month is $36 a year. On a $300 balance that is 12% a year, before the portfolio has earned anything. On $3,000 it is 1.2%. On $30,000 it is 0.12%, which is cheaper than most percentage-based alternatives. The same product is expensive or cheap depending entirely on how much you hold.

Put side by side, with the same balances run through two typical percentage fee levels (illustrative fee levels, not any named provider’s pricing):

Balance	Flat $3 a month	0.25% a year	0.75% a year
$300	$36 — 12%	$0.75 — 0.25%	$2.25 — 0.75%
$3,000	$36 — 1.2%	$7.50 — 0.25%	$22.50 — 0.75%
$30,000	$36 — 0.12%	$75 — 0.25%	$225 — 0.75%

Annual cost in money, then as a percentage of the balance. The flat fee is the most expensive option at $300 and the cheapest at $30,000. The break-even point against a percentage fee is the annual flat fee divided by the percentage: $36 ÷ 0.75% = $4,800, and $36 ÷ 0.25% = $14,400. Below those balances the flat fee costs more; above them, less.

The practical consequence: subscription apps are worst precisely where they are marketed hardest — at people starting with very small amounts. That does not make them wrong to use; the habit they build may be worth more than the fee costs. But it should be a decision you make with the number in front of you, not one made for you by the phrase “only $3 a month”. Our investment return calculator makes this visible: enter your starting balance, your monthly contribution and the fee as a percentage of your balance, and it shows what that fee costs in money over the whole period.

The Costs That Are Not the Headline Fee

“Commission-free” has become the default, which means the interesting costs moved elsewhere:

• Currency conversion. Usually the largest cost for anyone buying foreign shares, charged on the whole transaction rather than on any gain. Two apps advertising identical commissions can differ several-fold here.
• The spread. The gap between buying and selling price, paid on both entry and exit, never itemised on a statement.
• Payment for order flow, securities lending, uninvested cash. How several commission-free apps actually earn. Not sinister, but it explains why the service is free and occasionally why execution is not the best available.
• Withdrawal, transfer-out and inactivity fees. Small, and they arrive at the moment you want out.
• Fund charges inside the portfolio. Separate from anything the app charges, deducted before you see a return.

A useful test: price one realistic year — your actual contributions, in your actual currency, including getting the money back out — rather than comparing headline fees.

Fractional Shares, and What “Start With $1” Really Means

Fractional shares let you buy part of a share, so a high share price no longer excludes small investors. That is a genuine improvement and it is why almost every app now advertises a tiny minimum.

Two things the marketing leaves out. First, a fraction is usually held by the broker on your behalf rather than registered to you, which can affect voting rights and how transfers to another broker work — some brokers cannot transfer fractions out and will sell them instead, realising a taxable event you did not choose. Second, a very small balance makes fixed costs dominate, as above. Starting small is sensible; starting small in a product with a flat fee is a different proposition.

Availability Eliminates More Options Than Features Do

Most apps discussed online are open to residents of one or two countries. An investment app is a regulated service, so it operates where it is authorised — and being able to download it tells you nothing.

Check, in this order: whether it accepts residents of your country; which legal entity you would contract with (a global brand often onboards different countries through different entities, with different protection); what identification it requires; and whether it supports any tax-advantaged account available where you live, since that usually matters more to your net outcome than the commission. Our guides by country cover the markets we research.

What Protection Applies — and What It Is For

Investor compensation schemes exist to return your assets if the firm fails and cannot return them itself, up to a statutory limit. They are not insurance against investments losing value, and no scheme anywhere covers that. Deposit insurance is a separate thing again and covers bank deposits, not investments.

So the question worth asking is not “is this app safe” but three narrower ones: which entity holds my assets, which regulator authorises it, and are client assets segregated from the firm's own money? All three are answerable from the provider's terms and the regulator's public register in a few minutes.

How to Narrow the Field

• Can it accept me where I live, and through which entity?
• Do I want to choose holdings myself, or have that done to a rule?
• What is the total annual cost at my balance — flat fee, percentage, fund charges and conversion together?
• Does it support the account type and any tax wrapper available to me?
• What happens if the firm fails, and can I transfer out in kind rather than being forced to sell?
• Only then: interface, research tools and how the app feels to use.

The first three eliminate most candidates. The rest is refinement.

Flat Versus Percentage Over Time: a 20-Year Example

The table above is a snapshot. Real balances grow, and the ranking between fee structures changes as they do. Take a plan that starts with $1,000 and adds $100 a month for 20 years, at an assumed 6% a year before fees (an assumption for illustration, not a forecast):

Fee structure	Value after 20 years	Cost of fees
No fees	$48,551	—
Flat $3 a month	$47,191	$1,360
0.25% a year	$47,073	$1,478
0.75% a year	$44,267	$4,284

The flat fee costs 12% a year of the balance in the first months — yet over the full 20 years it ends up costing about the same as the 0.25% fee, and far less than 0.75%. The reason is the break-even arithmetic above: this plan passes the $4,800 break-even against 0.75% during its third year and the $14,400 break-even against 0.25% during its ninth, and from then on the flat fee is the cheaper of the two in every month.

Two lessons follow. A flat fee is a poor deal for a small balance that will stay small, and a reasonable one for a balance that will grow. And the size of a percentage fee matters enormously over long periods: the difference between 0.25% and 0.75% here is nearly $2,800, with nothing else about the plan changed.

Our investment return calculator runs the percentage-fee version of this on your own starting amount, contribution, return and fee, and shows the fee’s cost in money. To test a flat fee there, convert it to a percentage of your expected average balance.

How to Compare Fee Structures Yourself

1. Write down every layer of cost: platform or subscription fee, fund charges inside any fund you would hold, currency conversion, and any withdrawal or transfer-out charge.
2. Convert them to one unit. Annual money at your current balance is the simplest: a flat fee is fee × 12; a percentage fee is balance × rate.
3. Find the break-even between any flat and percentage option: annual flat fee ÷ percentage rate.
4. Look ahead. If your balance will grow past the break-even within a few years, weigh the long-run cost, not today’s.
5. Price the exit. A cheap platform that charges heavily to transfer out or to convert currency can cost more over a full round trip.

Sources

This page is written from the primary sources below — the providers’ own published terms and pricing, and the relevant regulators’ own published material. Links were last confirmed to load on September 19, 2026. Providers change their terms without notice, so treat anything specific here as a starting point and confirm it against the source before acting on it.

• SEC Investor.gov — fractional shares
• SIPC — what SIPC protects (and what it does not)
• FDIC — deposit insurance: what is and is not covered
• FCA Financial Services Register — check a firm