My old broker (maybe 15 years ago) said that after hours market trades were made if a broker (examples; Morgan Stanley, Schwab, Fidelity) had an "in house" match up of buyers and sellers. They were the market maker and made the trade after hours if both sides had open positions during after hours. I think that is what he said. Again this was many many years ago. Just wondering to your knowledge how does it work today?? Do after hours bid/asks go to a in house routers? Does it stay with the in house broker? Does it go to many routers and many brokers? Could you end up with odd lots (stocks) in an after hours trade? Do I have to get an OK from my broker to (in the future) enter into after hours trades?? Was watching TSLA today at the end...Was curious what it would do after hours...