all of the following taxpayers are u.s. citizens. none of them are dependents. which is required to file a 2021 income tax return? sal (62), married filing separately (mfs), $3,500 gross income. ariel (50), qualifying widower (qw), $18,550 gross income. fred (32), head of household (hoh), $17,500 gross income. clarisse (75), single (s), $12,575 gross income, all from wages.