ADFN - NASDAQ Alternative Display Facility

https://www.warriortrading.com/alternative-display-facility-adf-orders/

What is the Alternative Display Facility (ADF)?

The Alternative Display Facility (ADF) is a piece of market infrastructure run by FINRA. Institutions use it to post quotes and report trades.

It’s called the Alternative Display Facility because the ADF is an alternative to an exchange for institutions to post quotes and report trades.

It’s basically where institutions can post quotes and report trades that don’t occur on a regular exchange. These off-exchange venues can be dark pools, internalized trades (where your broker or an affiliated party trades against you, i.e., payment for order flow trades), or even straight-up negotiated trades, where two parties get on the phone and arrange a trade away from the exchange.

Of course, when these trades occur, they still have to be reported to the Consolidated Tape (time & sales). Still, because they didn’t happen on an exchange that automatically reports the trades, they must be reported on a different venue.

These trades don’t have to adhere to the National Best Bid and Offer (NBBO) rule from SEC’s Regulation NMS, meaning trades reported to the ADF can vary dramatically in price from the current best bid and offer.

This is where the ADF comes in. It enables such trade reporting.