IEX offers a Discretionary Peg™ (D-Peg™) order type which is a non-displayed order that is priced at either the National Best Bid (NBB for buys) or National Best Offer (NBO for sells). D-Peg™ orders passively rest on the book while seeking to access liquidity at a more aggressive price up to Midpoint of the NBBO, except when IEX determines that the quote is transitioning to less aggressive price
How to Place a D-Peg Order
Please note, the IEX D-Peg order type is only available via the TWS version 961 and above. Instructions for entering this order type are outlined below:
Enter a symbol and choose a directed quote, selecting IEX as the destination. Right click on the data line and select Trade followed by Order Ticket to open the Order Ticket window.
Select the REL order type from the Order Type drop down menu.
Click on the Miscellaneous tab (Misc.) and at the bottom there will be a checkbox for "Discretionary up to limit". Check this box. The price that you set in the Limit Price field will be used at the discretionary price on the order.
Hit Preview to view the Order Preview window.
For additional information concerning this order type, please review the following exchange website link: https://www.iextrading.com/trading/dpeg/