Your post does not provide us with any details about your son. You have not mentioned whether he is a child for whom you received the child tax credit or if he is older than 16, a college student, etc. etc. You seem to indicate that your original tax return claimed him as a dependent, and now you are amending to remove him as a dependent. That change could affect several things including your filing status. If your son was your only qualified dependent then your filing status might change from Head of Household to Single, making more of your income taxable. If you received child-related credits like earned income credit or child tax credit, those have to be paid back to the IRS when you remove him as a dependent.
Without giving any personal information like your SSN or email, etc. provide some details so we can be more helpful and explain why you may owe tax due now.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
