Why did I get charged another commission after I modified my order?

In the case of a spread order, each leg of the spread is treated as an independent order for commission purposes. Using a diagonal spread involving a short XYZ June 100 strike call and a long June XYZ 100 strike call as an example, a separate commission would be charged for each of the contracts as if they had been executed as separate orders…

If you do not modify an order in between partial fills and the order is executed within the same trading day, then the commission will be applied as if the order were a single fill with regard to commission minimums.

However, orders such as a GTC (Good-til-Cancel) order that persist overnight will be considered a new order the next day for the purposes of determining order minimums…

IBKR offers two types of commission structures: Fixed and Tiered.

For the Canadian market, IBKR's Fixed stock commission rate is CAD 0.01 per share with a minimum of CAD 1.00 per order. Commissions are capped at 0.5% of trade value, plus the applicable…

For European stock Algo orders, IBKR will apply the commission cap (or maximum commission per order) as follows:

• EUR-denominated stocks: for every EUR 75,000 of executed value a new per order cap (or maximum commission per order) will be applied…