Yes, you would have to file an amended return for your son so he would be able to claim and get the exemption for himself. Before you do that, please double check the conditions that the IRS have below for another person to be able to claim their children, and if it matched what you have learned go ahead with the amend.
A parent may claim their child if they meet either the qualifying child or qualifying relative test as
outlined below:
Qualifying Child
These 5 tests (all of
them), will qualify a child as a dependent:
-
Relationship: They must be your child,
adopted child, foster-child, brother or sister, or a descendant of one of
these (grand or nephew).
-
Residence: They had to live with you
in the same residence for more than half the year. Being away at school is
considered as living at home.
-
Age: Must be under age 19 or
under 24 and a full-time student for at least 5 months of the year. They
can be any age if they are totally and permanently disabled.
-
Support: child did not provide more
than half of their own support during the year.
-
Joint
Support: The child
cannot file a joint return for the year.
Qualifying Relative
These 4 tests (all of
them) will qualify a relative as a dependent:
-
Not
Qualifying Child: They
are not your or another taxpayer’s “qualifying child”
-
Gross
Income: Dependent
has to earn less than $4,050
in 2016.
-
Total
Support: You
provide more than half of
the total support for the year.
-
Member
of Household or Relationship: The
person (a friend, girlfriend, non blood relative) must live with you all year as a member
of your household or be one of the relatives that doesn’t have
to live with you (mother, father, brother, sister, aunt, uncle,
stepmother, stepfather, your child, stepchild, foster child, adopted
child, etc) Note: this list is not all inclusive.
Here is the LINK that will help you get started with your son's amended tax return.
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
