What is taxable income and how do you know how much taxes are owed?

By completing your income tax return correctly.

Start with all of your total worldwide income then subtract the adjustments to your income to come up with your adjusted gross income on the 1040 tax form line 37 and 38.

If you can qualify for some of the adjustments to income on the 1040 tax return those amounts would reduce you're your total income to make up your adjusted gross income line 37 and line 38 of the 1040 tax form and in turn reduce your taxable income and your federal income tax liability. Then you will subtract your deduction amount and then your exemption amount and line 43 you will have your taxable income. Then you will be able to determine the amount of your federal income tax liability for the year that and that amount will end up line 44 page 2 of the 1040 tax form.

Go to the IRS.gov web site and use the search box for Instructions 1040 in Adobe PDF Format go to page 29 through page 35 Adjusted Gross income start with line 23 through line 36 of the 1040 tax form then go through lines to line 44 for your taxable income on your 1040 federal income tax return.