I assume it’s based off the weird IRS rule where they stop qualifying for the $2000 child tax credit when they turn 17.
This is my understanding as well.
Here's a portion of a write-up I did for work. It's about a week old. The link is helpful. "DR" = domestic relations cases (i.e. divided homes where there's likely some sort of custody order). I did the research with through this lens so ignore some of that specific nuanced stuff to family law. Also, none of this constitutes legal advice and if you have specific issues you should contact a CPA or lawyer in your jurisdiction.
Who: From what I can gather, the majority of adults who fit under the thresholds for income will qualify and don’t have to do anything. I’d note that any undocumented or unapproved immigrants do not qualify. For calculating the benefit I found a easy-to-use interactive chart here:
https://smartasset.com/financial-advisor/coronavirus-stimulus-package. The link also provides a nice overview of the stimulus package. Now, key for DR, it appears that in divided family homes the additional child benefit will go to the parent who claimed that the child in the prior tax year on record (be that the 2019 returns if the parent is on top of it and filed already or, in the likely event he or she hasn’t, 2018 return). Continuing with the DR perspective, I see some serious unfairness issues with that because usually the parents alternate years and, as such, the parent who receives the money will arguably be getting an unfair windfall. Additionally, AZ uses a pro-rata formula for figuring out each parent’s financial responsibility to a/the child(ren) so I can see an argument where the primarily financially responsible parent would claim he or she should get the primary benefit. Lastly, this is going to be a mess for parents who got divorced this year and haven’t yet filed 2019 taxes or did so jointly. Unfortunately, I don’t see any safeguards with the Act itself or any sort of guidance on the issue. And, it looks like for those who haven’t filed a 2018 or 2019 return they cannot get the stimulus check until they do so.
What: Generally, it’s a one-time $1200 payment and $500/child. But, at certain thresholds it decreases $5 per every $100 in income and cuts off at a particular limit (including the child bonuses). Again, see the link above
When: Reports I’m reading indicate that payments may have already started as early as April 9, 2020 but should disperse electronically within that week with paper checks being cut thereafter. This payments should be automatic by the federal government.
Why: There’s probably a political answer to this that isn’t worth getting into.
How: From what I can gather, basically an individual’s or married couple’s most recent tax returns will serve to identify who gets money, the income to consider, the identified dependents for the filer (again, for the additional $500 kid bonus), and whether the payment will be made electronically or by mailed check as payment will be made in the same form and fashion as the person got his or her last tax return. For those where there are some logistical issues, I’ve read that the federal government will be creating an online portal for those people to go on to try to apply directly (and likely fix whatever glitch caused the problem – like a new address that wasn’t forwarded or a canceled bank account).