You can add your boyfriend as your dependent under the "qualifying relative" rules if he qualifies.
To qualify,
- He can't be claimed as a dependent by someone else.
- He must be a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
- He lived with you the entire year.
- He made less than $4,300 in 2020.
- You provided more than half of his financial support.
If your boyfriend is receiving Social Security Disability benefits, being a dependent on your tax return should not cause his benefits to decrease. Per the SSA, benefits would decrease or stop if he started working at a level that was considered "substantial" or if it is decided his medical condition has improved to the point that he is no longer disabled.
For more information, please see the SSA website Your Continuing Eligibility.