dear.some brokers dont allow scalping bcoz the chances of loss is high during scalping since we take only 5 pips or 10 pips. so once u loss many times u will dont have the hope of trading in forex and u will leave forex permanently and then broker cannot make money from u in spreads. but if traders lost then brokers will get profit because they didn't need to pay. can have the good scalping tradign send order to the inter bank regularly so if some one make profit from the trade then broker pay from his pocket, Broker think that all traders will loose amount so he collect that amount without sending information to interbank, so they don't allow scalping make the dolar as well