After you file

I am not sure I understand your question.  Are you preparing your son's tax return?  Where his income goes, depends on the type of income.  In certain circumstances, it will be reported on your tax return.  (investment income over a certain amount)

If you are reporting Investment Income see the attached file for instructions.

First is your son, who is 19, still in school (college) and are you claiming him as a dependent?

Even if he is a dependent, he will generally need to file a 2017 tax return if his:

  •  earned income (money made by working) exceeds $6,350, or
  •  unearned income (interest, dividends, capital gains, etc.) exceeds $1,050, or
  •  business or self-employment net income (gross minus expenses) is at least $400, or
  •  gross income (earned plus unearned) exceeds the larger of $1,050 or your earned income (up to $6,000) plus $350.

Even if his income falls below these filing requirements, he may want to file to get any taxes that were withheld from his paychecks.

If he has Investment Type Income  between $1050 and $10,500  see attached instructions.