No -- clients would never receive a worse execution price than the current National Best Bid/Offer (NBBO) or its equivalent and will still have the opportunities for price improvement that they have always had. However, clients that “opt-out” of internalization would lose another source of (i) potential price improvement or (ii) the opportunity to fill a trade without venue fees (in either case, internalization). Since IBKR will only execute with its affiliated internalizer when the customer is either benefited by, or indifferent to, the outcome as compared to the best alternate execution, the effect of opting out will generally be to forego an opportunity for further improved execution quality.
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