IB Commission depends on the spread for the instrument your client is trading with, but since some accounts have special spread conditions, there are additional rules for calculating the commission.
Zero Spread account has a fixed commission per trade and no spread, which makes it impossible to calculate the IB commission the usual way. Instead, it is calculated the following way:
IB Commission = Lot Volume * Zero Spread Commission * Level multiplier, where
- Zero Spread Commission is a fixed commission per lot on the Zero Spread account. The full table can be checked here: Zero Spread account, trading conditions.
ECN account also has a fixed commission, but it also has lower spreads than the Standard account, making calculations as follows:
IB Commission = Lot Volume * (Spread * Level Multiplier + ECN Commission * Level multiplier), where
- ECN Commission is a fixed commission of $6 per trade on ECN account.
Micro account has a fixed spread per each instrument, so the IB commission will not be changing based on the spread and is calculated the same way as on the Standard account.
You can check fixed spread rates in this article.