Interactive Brokers pricing: the free tier is priced, and IBKR wrote down where
IBKR Lite charges zero commission on US stocks. IBKR's own order routing disclosure states what that costs instead, in one sentence that most comparisons never quote.
Interactive Brokers sells two versions of the same brokerage account, and the choice between them is presented as a pricing question. It isn’t. From IBKR’s own routing disclosure, form 3074:
These offerings are designed to give IBKR clients the flexibility to prioritize the opportunity for zero-commission NMS stock trades and fixed-rate commission US equity option trades versus the amount and likelihood of price improvement they receive on trades.
The firm is not describing two prices there. It is describing a trade between paying commission and getting better fills, and it says so on its own first page.
What each side actually does
IBKR Pro sends orders to SmartRouting, IBKR’s own execution system, which scans competing market centres and routes for the best available price. The disclosure says SmartRouting “retains control over the routing of your order for execution and does not deliver your order for another broker to route.”
IBKR Lite does something different. Its orders “are generally routed to select over-the-counter market-makers”, and IBKR’s agreements with those market makers “provide Interactive Brokers payment for order flow.”
Then comes the sentence that decides the whole comparison:
reduced price improvement on executions received by IBKR-LITE clients
That is IBKR describing the potential effect of those payments, in proportion to the payment it receives. Not a critic, not a competitor. The firm.
Zero has exceptions, and they are listed
Lite’s zero commission covers NMS stock orders, with carve-outs stated in the same document: certain order types, orders executed at the open or close, orders outside regular trading hours, and stocks trading under $1.00.
A trader who works the open and the close, which is most of the day’s volume, is therefore paying on exactly the orders that matter most. That is not hidden, and it is also not on the marketing page.
The clause almost nobody has read
Buried in the same section:
If IBKR detects certain non-retail trading behaviors from an IBKR-LITE client, IBKR will route their non-marketable orders to lit exchanges rather than to market makers.
IBKR reserves the right to decide that you are not behaving like a retail client and to change your routing accordingly. The firm does not publish what triggers it.
For anyone choosing Lite because they trade actively, that clause is worth more attention than the commission table. It suggests the free tier is designed for order flow that market makers want, and that flow is not the flow an active trader produces.
What Pro costs, per share
US stocks, from IBKR’s own commissions page, for monthly volume up to 300,000 shares:
| Per share | Minimum per order | Maximum per order | |
|---|---|---|---|
| IBKR Pro, Fixed | USD 0.005 | USD 1.00 | 1% of trade value |
| IBKR Pro, Tiered | USD 0.0035 | USD 0.35 | 1% of trade value |
| IBKR Lite | USD 0.00 | none | none |
Fixed is described as all-inclusive, covering exchange, clearing and regulatory fees. Tiered quotes a lower rate and adds those fees separately, so the two are not comparable at face value. Margin loans start at 4.13%.
IBKR’s own worked example on that page: 100 shares at USD 25 costs USD 1.00.
The crossover is half a cent, and it does not move
The minimum makes the per-share cost of Fixed vary at small sizes and then stop varying:
- Below 200 shares, the $1.00 minimum binds. At 100 shares you pay a full cent a share, at 50 shares two cents.
- At 200 shares, $0.005 × 200 is exactly $1.00 and the minimum stops mattering.
- Above 200 shares, you pay a flat half a cent per share, whatever the size.
That last line is what makes the comparison decidable, because forgone price improvement also scales per share. Above 200 shares the whole question collapses to one number:
does SmartRouting find you more than half a cent per share?
If it does, Pro is cheaper at any order size, and a bigger order does not change the answer. If it does not, Lite is cheaper at any size. The crossover is not a dollar figure that moves with your order value; it is a rate, and it sits at $0.005.
Below 200 shares the arithmetic tilts toward Lite, because you are paying up to two cents a share for routing that would have to be very good indeed to repay it.
How to decide without guessing
Find your typical share count, not your typical dollar amount. Share count is what both sides of this are priced in, and dollar value tells you nothing on its own.
Read IBKR’s own execution statistics rather than anyone’s summary, including ours. The disclosure points to the firm’s quarterly order routing reports, and price improvement per share is the figure to look for. That is the only number that settles the half-cent question with data instead of argument.
Decide which question you are answering. If you are buying and holding, commission is the whole cost and Lite is cheaper. If you trade size or frequency, execution is the larger number and it appears on no pricing page.
This is the same structural point we set out in how brokers make money: when a service is free, the payment moved somewhere you are not looking. IBKR is unusual only in writing down exactly where.
What we checked, and what we didn’t
Everything above comes from IBKR’s form 3074 dated 16 April 2024 and its published commissions page, read on 17 August 2026. We have not opened an account, compared fills, or measured price improvement on either offering.
The disclosure describes a potential effect, not a measured one, and IBKR publishes execution statistics that we have not analysed. Anyone claiming to know the dollar cost of Lite for your order size should be asked which report they took it from.
Sources
- Interactive Brokers — Order Routing and Payment for Order Flow Disclosure, form 3074, 16 April 2024
- Interactive Brokers — commissions