How old does a child have to be to claim on income tax return?

Question

whats the age limit

Answer 1

He just has to be born before the end of the year to be claimed on that year's return.

Answer 2

If the child is born alive before midnight on Dec 31, they can be claimed as a dependent for the year, even if they might have only lived a minute or two during that year.

Answer 3

I think you meant "how young", and it depends on whether they are a student:

"In general, to be a taxpayer’s qualifying child, a person must ...
must be under the age of 19 at the end of the tax year, or under the age of 24 if a full-time student for at least five months of the year, or be permanently and totally disabled at any time during the year. "