my son is 17 and lives at home. So, he is still a dependent of mine. I tried to file and It says I cannot claim him because he did his own. Do we need to amend his?

Unfortunately you will need to file a paper return because there is no way to get around the e-file system once your dependent has already filed and claimed themselves.  Paper file with your dependent included on your return.

This article will give instruction on how to print and mail your return.

Your dependent will need to amend their return to indicate someone else is claiming them.

See this TurboTax FAQ for help with amending.

You cannot get the child tax credit for a 17 year old; instead you get the $500 credit for other dependents.   But he can be claimed as a dependent.   On his own tax return he MUST say in MY INFO that someone else can claim him as a dependent.  So....he made a mistake and now you are stuck with having to file on paper and mail your return.  He will have to amend his return after it has been fully processed.   You do not have to wait for him to amend-----print, sign and date your return that claims him, and mail it in.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.