You must file a tax return if your gross income is above the filing thresholds. The filing thresholds vary depending on your filing status and age.
Gross income means all income a person receives that is not exempt from tax. This includes income from sources outside the US and from the sale of a home, even if you can exclude part or all of the sale.
Dividends received, even if reinvested are considered income.
The 2023 filing thresholds are as follows:
$27,700 Married filing jointly and both spouses are under 65
$29,200 Married filing jointly and one spouse is 65 or older
$30,700 Married filing jointly and both spouses are 65 or older
These filing thresholds will increase slightly for the 2024 year