My son turned 17 on Nov. 31, 2017 do I put him down as 16 on my 2017 tax’s return

[DoninGA]

You enter his date of birth in the dependent section of My Info.  Since he was not under the age of 17 on the last day of 2017 he is not eligible for the Child Tax Credit on the 2017 tax retun.  Just because he is 17 does not mean you cannot claim him as a dependent on your tax return and use his personal exemption.