Your gross income (again, this differs from your AGI) includes income from selling your main home and gains (but not losses) reported on Form 8949 or Schedule D and from sources outside the US.

Your gross income doesn’t include any Social Security benefits unless:

⦁ You’re married but filing separately and lived with your spouse at some point in 2019.
⦁ Half your Social Security benefits plus your other gross income and any tax-exempt interest is more than $25,000 filing single (or $32,000 if married, filing jointly).
⦁ If either of those is the case for you, you can check out the Instructions for Forms 1040 and 1040-SR or Pub. 915, Social Security and Equivalent Railroad Retirement Benefits to figure the taxable part of Social Security benefits you must include in gross income.

If you’re age 65 or older, you should file taxes under the following circumstances:

⦁ Single filer with at least $13,850 in gross income.
⦁ Head of household with at least $20,000 in gross income.
⦁ Married filing jointly (if one spouse is 65 or older, $25,700 in gross income; if both spouses are 65 or older, $27,000 in gross income).
⦁ Married filing separately (any age).
⦁ Qualifying widow(er) age 65 or older with at least $25,700 in gross income.
⦁ In the 2019 tax year, the IRS introduced Form 1040-SR, US Tax Return for Seniors. This form is basically the same as Form 1040, but has larger text and some helpful information for older taxpayers.