An adult that lives with me and that I support financially is, married but separated for years, can I claim that person?

[brysonlaike]

the person is married but has been separated for over 4 years.

[xmasbaby0]

You have not told us some of the other important things we need to know.   Is the adult related to you in any way?   Did they live with you for the whole year in 2021?   Did they have any income?   How much income did they have---NOT counting any Social Security?

[Mike9241]

not enough info tou can claim the adult if they 

• Lived in your household for the entire year. Temporary absences are permitted.
• Their gross income for 2021 is less than $4,300
• you provided over ½ their support

[rjs]

If the adult files a joint tax return with their spouse, you cannot claim them as a dependent. In some cases they could file jointly, even though they are separated, depending on exactly what kind of separation they have.