US Direct API stock orders (does not apply to US smart API orders)=USD 0.12/Cancel or modify order.
From what i read above , there's a fee only when you modify or cancel a stock order with a specific destination and through API.
No fees when you modify or cancel an order sent via Api to smart or directly on tws.
There's also an execution credit.
I'm not an English native speaker, so maybe I'm misunderstanding
what I read, if this is the case I apologize in advance.