If someone claimed you as a dependent on their tax return, you are not eligible for a stimulus payment. If you met the requirements to be claimed by whoever claimed you, there is nothing you can do about it because if you meet the qualifications to be claimed, you can't claim yourself even if the person who could have claimed you chose not to claim you.
If you did not meet the qualifications to be claimed but were claimed mistakenly by someone, then you can file a return claiming yourself and print and mail the return. The IRS will sort out who could rightfully claim you at another time.
If you have already filed a return and need to change from checking the box to be claimed to unchecking the box, you will have to prepare, print and mail an amended return form 1040X to change your dependency status. The 1040X must be printed and mailed. It can't be efiled.
