Age Limit for Child Dependent on Taxes?

See this information for requirements of the child tax credit: turbotax.intuit.com/.../INF15610.html

This depends entirely on your circumstances. You need to contact your tax office. Here in Canada, there is a toll free number that you can phone that will put you in contact with someone who can answer your problem. Here we can claim them if they living at home, until they are 18. If they are full time students, they can be claimed until they are older. I am sure it differs in other countries.