Why can't I claim the Child Tax Credit this year?
The most common reason taxpayers who formerly got the Child Tax Credit no longer qualify – at all – is that their child turned 17 sometime in 2016.
As the credit is worth up to $1,000 per child, it's especially painful (in more ways than one) for parents of twins, triplets, quadruplets (etc.) who all turned 17 during the tax year.
See the full Child Tax Credit qualifications.