Simultaneous submissions?

Are you talking about submissions to theatre companies or submissions to playwriting competitions? As far as I know, it's okay to submit it to as many places as you like, as long as it has never yet been performed by anyone else.

Hope this helps.

Simultaneous submissions

Your work belongs to you. Submit it wherever you like.

If someone wants to produce or publish it, make a deal with that company on the terms that are mutually acceptable.

Depends on where you're submitting it. If it has never been produced, some companies want rights to the World Premier so they'll ask you to hold off on submitting it until they at least set a date for the premier. Otherwise, submit away!