Clients are not required to subscribe to market data through IBKR. If you choose not to subscribe to a paid service, delayed quotes will be supplied at no cost, where available. Furthermore, while the lack of real-time market data will have no effect upon execution quality, IBKR strongly recommends against trading without a source of real-time quotes to avoid mistaken or unpredicted trades.To guarantee that clients submitting orders are aware that they are not being presented with real-time quotes, IBKR will supply a warning notification at the point of order confirmation notifying the client of this fact. If entering orders using the API without a real-time quote feed, a warning will also be activated.For more information, see: How do I subscribe to market data from the TWS?