Your age doesn't matter. All your income taxable. Are you asking about the RMD Required Minimum Distribution? When you turn 73 you have to start taking the RMD from your IRA and 401K accounts. You will get a 1099R at the end of year for each one.
Are you asking about Social Security? At any age up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0
Or are you asking about a state return?
