How much taxes does a 19 year old have to pay?

When your income tax return is completely correctly then you will know the amount of your federal income tax liability.

This answer will only be known after you determine the amount of your gross income that will be taxable income to you on your income tax return.

For an example if you are a qualifying dependent on another tax payer's income tax return and you have 951 of unearned income your federal income tax liability would be $1 in federal income taxes. Interest, dividends, capital gains, rental income, gambling winnings, etc.

If you have 5700 of gross earned income wages, salaries, tips, etc. from an employer added to the 951 of unearned income on your 1040 income tax return then your federal income tax liability amount on your 1040 income tax return would be $96.

If you are a self employed taxpayer and have a net profit of 500 from your schedule C-EZ and schedule SE added to the above amounts then your federal tax liability would be income tax $141 plus yourself employment tax of $70 for a total amount owed of $211 when your 1040 income tax return is completed correctly