Anyone who is a citizen of the USA is required to file and pay taxes on their worldwide income, no matter where they live or earn the money. There are rules that allow many retired citizens to have an income liability of zero. For many it just got a little better in 2019 for 2018 income taxes.
Going forward single taxpayers will have a standard deduction of $12,000, and if you turned 65 or are older than 65, then your standard deduction is $13,600. This means that if your adjusted gross income is equal to or less than the standard deduction, no tax is owed. The tax laws get more complicated when calculating the amount of Social Security benefits which are taxable. The general rule is that if one half the SSA income plus other non-social security income (interest, dividends, pensions etc) is $24, 000 or less, then none of the SSA is taxable.
For example, a citizen who receives $1,500/month in SSA benefits plus $1,000/month in pensions or investment income would owe no income taxes. The total SSA for the year would be $18,000, the total other income $12,000. One half the SSA ($9,000) plus the other income, $12,000, gives a total in calculating taxable SSA of $21,000. Since this is less than $24,000, none of the SSA is taxable, so the adjusted gross income is only $12,000. So no matter how old the citizen is, the tax liability is $0
For married filing joint returns the standard deduction is $24,000, $25,600 If one of the filers is 65 or older and $26,600 If both are 65 or older. The amount to use to calculate how much, if any, of the SSA is taxable is $32,000 Instead of $24,000. I will give an example of married filing joint and the calculations involved in a future post.