How can I find out if my mother claimed me as a dependent on her taxes ?

Whether she did or not, if she CAN legally claim you, you can't claim yourself.

You can't access any information about her tax return - except if she chooses to show it to you. if you're entitled to claim yourself on your own tax return, then file it doing so. The question isn't who "wants" to claim you - the question is who is ENTITLED to claim you. See IRS Publication 501.

File and claim yourself and see what happens.

You really can't. Your only option is to ask to see her copy.

You can't claim yourself...............

You go ahead and file to get back your tax and if there is a discrepancy you will be notified, or she will.

If you efile and it rejects then you were already claimed.

You can try and efile your own claiming yourself. If you get rejected, then someone claimed you. You cannot find out who.

If she can claim you, she can claim you and you cannot claim yourself even if she does not.

How old are you and how much money did you make and are you a student?

if your return is rejected due to already being claimed on another tax return, IRS will tell you by that rejection
you both cannot claim your personal exemption, if she did and filed ahead of you, if you tried to efile it would have been rejected immediately since your # had already been claimed
if you filed your own tax return, if you get the refund you claimed on the return, apparently nothing was amiss with yours and your mother's tax return

Technically, it doesn't matter. What matters is whether she can claim you, not whether she did. If the law said allows her to claim you, then you must do everything exactly the same as if she did claim you, even if she decided not to claim her. If the law says that she can't claim you, but you think she did anyway, then fill out your taxes as though she didn't claim you, but send them on paper, by mail, in an envelope, with the proper postage, and not electronically or online.

You cannot file "with" her - jointly. That would be illegal and - well, you have to file your OWN taxes. She is entitled to claim you if you are living under her roof. This should not concern you.