I'm sorry for your loss.
If your child met the usual requirements to be a dependent (lived in your home, under age 19 or under age 24 while being a full time student, and so on) then he can still be your tax dependent in the year he passed. In the Dependent Interview, select "The whole year" for how long the child lived in your home (unless you shared custody with another parent who you are divorced or separated from. In that case, select "the whole year" only if the child lived in your home more than half the days he was alive in 2018.)
If your child was born AND died in 2018, you can claim him as a dependent but he needs a social security number. If you don't have an SSN, you may need to use a fake SSN to pass the interview in the program. Print the tax return, white out the fake SSN if you used one, and attach copies of the birth and death certificate to your return, and mail it in.
Dependents are generally eligible for either a $2000 or a $500 tax credit. A child dependent may also qualify you for earned income credit. If you paid for child care so you could work, you can use the Child and Dependent tax credit.
Your child's SSN is probably blocked from e-filing. If so, print your return, write "deceased" and the date next to his name, and sign and mail your return. Don't forget to also print and mail your state tax return, since it can't be e-filed if you don't e-file your IRS return.
