No you won't be charged multiple commissions within a day. AON is way harder to fill - say you put in an order to buy a penny stock at a certain price - a day order - say it is for 500,000. If they fill the first 100k and the rest does not fill you get charged the one commission. If they continue to fill it in partial orders all day - say another 100k at a time it is still one commission AS LONG AS YOU DON'T CHANGE THE TERMS OR THE PRICE. If you don't change that order it is good all day for one commission. The commission is good for the entire day.