It&#x27;s a good question.  If you are a retail trader, you should almost always use limit orders.<p>You can never get a worse fill than what you ask for but the internalizer can make money off your order and you can miss out on market moves that occur in the second after you place your order.  if you are fine getting price that you put your limit order in for then as far as you are concerned, you&#x27;ll be fine.<p>As with all things market micro structure related, nanex.net has a good writeup on this.
I&#x27;m not sure  how often this scenario occurs as I&#x27;ve never worked for an internalizer but its<p><a href="http:&#x2F;&#x2F;www.nanex.net&#x2F;aqck2&#x2F;What-Every-Retail-Investor-Needs-to-Know.pdf" rel="nofollow">http:&#x2F;&#x2F;www.nanex.net&#x2F;aqck2&#x2F;What-Every-Retail-Investor-Needs-...</a><p>Check out the section called &quot;Marketable Limit Orders&quot;.<p>&gt; For example: the Wholesaler receives a retail order to buy 2000 shares at $10.03 or better (lower)
when the SIP shows a total of 2000 shares offered at the best offer price of 10.01.<p>1. Wholesaler buys 300 from one exchange at $10.01, and immediately, 1700 shares that were available on other exchanges disappear, causing the best offer price to move to $10.02.<p>2. Wholesaler buys 400 at $10.02, and again, sell orders on other exchanges disappear,
causing the best offer price to move to $10.03.<p>3. Wholesaler sells short remaining 1300 shares at $10.0290 to retail investor, providing a $0.0010 price improvement relative to the $10.03 SIP offer price at time of execution.<p>4. Within seconds, stock reverts back to $10.01 offered.<p>5. Wholesaler covers short by buying 1300 shares at $10.01.<p>&gt; By quickly influencing the price of the stock, perhaps by less optimal routing, then directly filling the order at an execution price away from the original NBBO at time of Order Receipt, the Wholesaler profits from the $0.019 change on 1300 shares ($24.70), less any &quot;price improvement&quot; given to the retail investor, less the $4.00 Payment for Order flow paid to the Retail Broker (2000 shares x .0020 per share) and $6 in exchange fees (maximum SEC fee $0.0030 per share x 2000 shares).