Submission History

It is necessary, because you would be surprised how many self-published authors and people who have already submitted to publishers then go ahead and try to find agents.

Tell them you haven't sent it to any publishers or editors, just agents. They just want to make sure you haven't blown all the chances at selling this. I don't think you need to give agent names unless you want to, and you've signed with them. I can't imagine why they'd care what other agents read it, as that doesn't affect the potential sale of the book. If you have multiple agents trying to sign you, they might want to know who they "beat out" out of curiosity, but there's no reason for them to know.

Agree with Danthia. I would also let them know if any other agents are currently reading the manuscript, though you don't necessarily have to say who.

Sorry, I didn't phrase my answer quite right. Danthia and ChaosTitan are right, you don't need to give them specific agent's names. They just want to make sure the book isn't already self-published or has been sent out to other publishers.

how tarnished?

If you've substantially revised a proposal/Manuscript (this is nonfiction) and retitled it, would an agent want to send it back to a publisher who saw it in its last incarnation?

I've signed with a new agent and have done the above with a project and am just wondering if those 12 pub are now going to be off limits for the new agent to send to?

It's likely going to be a hard sell since 12 publishers have already said no, but only your current agent can really answer this question. All you can do is ask. Mention the changes you've made and give him/her a list of the editors who've rejected it. Your new agent may know of some editors your old agent didn't submit to.

I usually query one agent at a time. I'm found out a long time ago that getting in a hurry in the writing and publishing games is futile.

If I run through a list of agents and get rejected, I'll send to publishers for a feel out.

But, trying to get representation first is better than going straight to the publishers, IMO. The agent can and will help you build a better book.

I'd tell the agent who you've sent it to, they asked, so tell 'um.