Robert is spot on. CS has routing deals that include price improvement and hidden liquidity. Most of the stuff goes through Citadel and SIG. They now use the old optionsXpress routing. The old deal was with UBS, but they pretty much saw UBS become not as competitive. Doesn't apply to SPX and VIX. The nice thing about routing deals is the firm will pretty much fix anything. Hidden liquidity - which IMHO shouldn't exist - means you might fill for size larger than display. This keeps the order from shipping.
Limit orders are mostly going to go to Maker/Taker platforms - marketable limits to to PFOF platforms. Schwab determines all routing with electronic - phone orders can be routed, but you pay a premium for phone service.
On rare occasion you won't trade with a MM and your order could be part of a customer cross, most likely on Maker/Taker venue. You can look at any firms SEC form 606 which shows routing - economics in terms of rebates.
The old oX platform is being folded into Schwab now for everything but futures.
Limit orders are mostly going to go to Maker/Taker platforms - marketable limits to to PFOF platforms. Schwab determines all routing with electronic - phone orders can be routed, but you pay a premium for phone service.
On rare occasion you won't trade with a MM and your order could be part of a customer cross, most likely on Maker/Taker venue. You can look at any firms SEC form 606 which shows routing - economics in terms of rebates.
The old oX platform is being folded into Schwab now for everything but futures.