The interest income is your child's income, not your own income. So, the question is does your child need to file a tax return?
Maybe. It depends on the amount of interest we are talking about here.
Assuming this is his/her only income :
-At or Under $1050? You don't have to do a thing. It is also not added to your return.-
-He/she must file if the interest (or other such unearned income) is over $1050. This doesn't necessarily mean he/ you will owe taxes, it just means a dependent return must be filed. Be sure to indicate that your child is claimed as a dependent on another return. If you are online, you will need to create a new account/ a new username to file your child's return.
If the child has enough interest/ unearned income that she/he is already required to file, then you may have the option to add it to your return using special rules.
Filing requirements for dependents can be found here:
https://www.irs.gov/pub/irs-pdf/p501.pdf
