A day trade is defined as opening and closing the same position on the same day. Margin accounts are allowed to have 3 day trades take place in a rolling 5 day period. A 4th day trade during this period would flag the investor as a Pattern Day Trader. Pattern Day Traders must start each day with at least $25,000 equity. Please read this additional FAQ about what happens when you are flagged as a Pattern Day Trader: https://support.tradier.com/article/155-what-happens-if-i-am-flagged-as-a-pattern-day-trader