@becflack A friend can be a dependent but they are not a qualifying person for Head of Household filing status. Your coworkers are incorrectly filing as HOH if they have similar situations.
IRS Publication 501 Dependents, Standard Deduction, and Filing Information page 9 - https://www.irs.gov/pub/irs-pdf/p501.pdf#page=9
Example 3—your friend. Your friend lived with you all year. Even though your friend may be your qualifying relative if the gross income and support tests (explained later) are met, your friend isn't your qualifying person for head of household purposes because your friend isn't related to you in one of the ways listed under
Relatives who don't have to live with you, later.
See Table 4.
