How is it possible for a trade to be executed by a broker but cleared by another broker?

External question — Personal Finance Stack Exchange Author: Flux Original post: https://money.stackexchange.com/questions/139744 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. The Interactive Brokers U.S. Microcap Stock Restrictions page says: Execution-only clients (i.e., execute trades through IBKR, but clear those trades elsewhere ) may not trade U.S. Microcap Stocks within their IBKR account. (IBKR may make exceptions for U.S.-registered brokers) How is it possible to execute trades through one broker, but clear the trade through another broker? When I buy a stock through an online brokerage, I don't see separate "execute" and "clear" steps. Instead, I just click on "Buy" and wait for my order to be filled. Under what circumstances will I need separate "execute" and "clear" steps, and why would I ever need to clear trades through another broker?

External answer — Personal Finance Stack Exchange Author: Joseph Casey Original post: https://money.stackexchange.com/a/139861 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. "Whereas the executing, or introducing, broker is hired by the customer and makes decisions about how to trade securities on the customer's behalf, the clearing firm performs critical back office duties to ensure that the transaction completes smoothly and successfully." According to https://medium.com/prooftrading/choosing-a-clearing-broker-43e230723fa8