I started doing my taxes and was going through the instructions for the federal form when I was stopped short by seeing this passage:
Kidnapped child. If your child is presumed by law enforcement authorities to have been kidnapped by someone who isn’t a family member, you may be able to take the child into account in determining your eligibility for head of household or qualifying surviving spouse filing status, the child tax credit, the credit for other dependents, and the earned income credit (EIC). For details, see Pub. 501 (Pub. 596 for the EIC).
This not something new, apparently. I looked back as far 2018 (the earliest year for which I still have instructions) and saw that it had been there but I had not seen it. I suspect that it goes back even further.
The rules for who can claim a child as a dependent and thus get a deduction or a tax credit is complicated by the fact that it depends on the time the child stayed with the tax filer. For example, both divorced parents cannot claim their child as a dependent. It depends on how the child splits their time between the two adults. A similar issue arises with foster children who may not spend the entire year with one family. That problem is common and so one can see the need for general rules to cover the various possibilities.
But how often does the kidnapped child problem occur? Often enough, apparently, that the IRS felt the need to create a rule to cover it. It is often the case that a kidnapped child has been taken by the non-custodial parent. But I would imagine that a parent whose child has been kidnapped would be far too distraught to care about whether that child can be claimed as a dependent.