When a trader make a trade with his broker, the broker has to cover the position in the market to protect him against exchange rate risk. Scalpers trade frequently sometimes making hundreds of transaction in a short span. Though the broker is getting income from the spread in these transactions, the frequent trades makes it difficult for the broker to correctly assess his position and cover it in the market. Moreover, the broker has to make frequent covering. Because of this many brokers are not preferring scalpers.

Scalping is allowed to every broker. The only problem is a broker provides some restrictions.