If you have a cash only account, you can buy and sell all you want. However, the amount sold must settle for three days before you can touch it again. Under a margin account, you can buy and sell, and your money will be available immediately to trade again. Now you have to have over $25k in your account to do this more than three times in a five day period. I know this for a fact, since I've been on 90 day restrictions many times. Very frustrating to say the least.