We are missing some information. Did your "significant other" have income and file a tax return? If so, then your SO is the one who should claim the mother as a qualifying relative. If your SO did not have any income or file a tax return, and you supported the mother, then the mother could be your qualifying relative dependent IF she lived with you for the entire year and she had less than $4300 of income not counting Social Security. For a qualifyng dependent claimed on a 2020 tax return you can get the $500 credit for other dependents and the 3rd stimulus amount. You cannot get the 1st or 2nd stimulus payments for a dependent over the age of 16, but the age limit changed for the 3rd one.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent
Be aware that claiming your SO's mother does not qualify you to file as head of household since the mother is not blood-related to YOU.
https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-cre...
Your SO's mother * might* be a qualifying relative that you or your SO can claim.
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, fiance (etc.) as a dependent on your 2020 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).
- No age limit for permanently and totally disabled children
• 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 $4300 (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?
•What does "financially support another person" mean?
•Can I claim a newborn baby?
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
