I trade in the U.S. stock market. I want to know how multiple orders and partial fills count towards getting flagged as a “pattern day trader”. I thought reaching the level of day trader was a good thing until I got slapped with a trading restriction. I don’t understand what is going on. Day trading buying and selling the same security within the same trading day. What if I process a series of buys on a particular security in the morning. Then sell them all in the afternoon like this:

Buy – Buy – Buy – Sell

Does this count as one day trade or three? What if either the Buy or Sell orders were partial fills?

My experience has been that a "trade" is considered to be the order and all of its fills. The number of fills is not something you can control and therefore is not your fault. The SEC is very clear that a pattern day-trader is supposed to be a real day-trader. Counting each fill would snare too many investors in their net.

From Rule 2520:
"The term "day[-]trading" means the purchasing and selling or the selling and purchasing of the same security on the same day in a margin account"

"The term "pattern day trader" means any customer who executes four or more day trades within five business days. However, if the number of day trades is 6% or less of total trades for the five business day period, the customer will not be considered a pattern day trader"

It's pretty clear to me that to "execute" a trade. I place an order and get fills. The order and the fills are a "trade". Now, if your two "buys" are based upon two separate orders, then the pattern you ask about would be two day trades.

So here’s a simple rule that will let you avoid being slapped with the pattern day trader penalty. Counting the number of day trades you make in a rolling 5 day period is a pain. Just do this. Any stock you buy, don’t sell it until the next trading day. If you hold every stock you buy at least overnight, you will never get hit with the pattern day trader penalty. You can even buy a stock a 1 minute until market close, then sell in 1 minute after market open the next day. Your total time exposure to the market is 2 minutes and yet you will never get hit with a pattern day trader penalty if you do this.

Your other option is to have a minimum of $25,000 in your account so that you can be designated as a real day trader. If you have a minimum of $25,000 in your account, you can make all the trades you want and you’ll never be hit with a penalty.