No. Your mother can claim you if you are 18 years old. You do not have to agree to it.
Here are the rules Mom can use--which make you a
qualifying child.
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, fiance (etc.) as a dependent on your 2019 taxes as long as they meet the following requirements:
Qualifying child
• They are related to you.
• They cannot be claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They are not filing a joint return with their spouse.
• They are under the age of 19 (or 24 for full-time students).
• They live with you for more than half the year (exceptions apply).
Qualifying relative
• They don't have to be related to you (despite the name).
• They cannot be claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They are not filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4200 (not counting Social Security)
• You provided more than half of their financial support. More info
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them.
Related Information:
• Does a dependent have to live with me?
CAN I FILE A RETURN IF I AM A DEPENDENT?
If you can be claimed as a dependent on your parents’ return, you can still file your own return so that you can receive a refund of taxes withheld. (You will not get back anything for Social Security or Medicare withheld.) Be sure that on your own return you say that you can be claimed as a dependent on someone else’s return.