examine your form 1040 after completing it. Look for the section marked "Amount You Owe"
Look on lines 22 and 23 of your Form 1040 for tax due for 2018https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing To see back taxes owed https://www.irs.gov/uac/view-your-tax-account