Yes. Doing so would make them eligible for the stimulus payment and any other eligible credits.
Yes if the other person also filed an incorrect tax return they have to amend. It is taking MUCH longer than the "normal" four months for the IRS to process an amended return. So if you are going through amending tax returns because someone is hoping for a stimulus check, it will not work out. There will be another chance to get stimulus money on a 2020 tax return if you made mistakes and did not file correctly to get it in 2020.
Note: If the person CAN be claimed as a dependent on someone else's tax return they must indicate that they can be claimed EVEN IF the other person does not end up claiming them.
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?