Fat Finger Protection

Fat Finger Protection allows customers to have orders rejected if the limit price on the order is priced too aggressively through the NBBO. Customers may configure Fat Finger limits using both percentage-based limits and dollar-based limits. Different Fat Finger limits may be specified across distinct limit price ranges to allow customers flexibility in setting up Fat Finger Protection. In a scenario where both a percentage-based limit and a dollar-based limit are specified, the least restrictive value will always be applied. Does not apply to RHO orders entered prior to the open until they move to continuous trading. The Fat Finger settings will be applied to both single leg and complex orders. Fat Finger Protection is not applicable for Stop Limit Orders. Fat Finger Protection is not applicable for floor-based Multi-Class Spread limit orders. Fat Finger checks are applicable to SPX versus SPXW and to SPXO versus SPXW* orders as they are eligible for electronic routing.

For Equities only, when the NBBO is unavailable, all orders with a limit price will use Last Sale as the reference price instead of the opposite side of the NBBO if the latter is not available. If Last Sale is also not available, the reference price will be the previous day’s Official Closing Price.

For Options only, if the opposite side NBBO is unavailable, no checks are performed unless during GTH. During GTH, the last best local displayed price will be used, or the previous day closing NBBO midpoint if that is unavailable.

For unpriced orders (excluding MOO and MOC), customers can specify to reject the order if the opposite side of the NBBO is not available upon order entry. This would apply to market orders, unpriced peg orders, and triggered stop orders as well.

*Effective 11/09/26