Understanding brokerage fees or commissions (one way, round trip?)

[hedgehog]

Brokerages just say their fees are $5, $10 or just 1$ (for Interactive Brokers).

However it is nowhere stated on any brokerage's site if said fee is one way, round trip (or you can never be sure) and when it is applied (buy or sell)? Ir is something I should know without a proper explanation?

Strange.

[Tortoise]

I've never seen a "round-trip fee" at a brokerage. They are typically "transaction fees," meaning one-way. So if you buy and then sell--whether immediately or years later--that's two transactions and therefore you're charged the transaction fee twice.