Jett and Cole are divorced, and each year they alternate who claims their five-year-old son Ed on their returns. In 2018, Jett claimed Ed as a dependent.
Assuming both of their incomes are below the threshold amount, if Jett doesn’t file a 2019 return before the economic impact payment is issued, he’ll receive $1,700 based on his 2018 filing, which is the $1,200 plus the $500 for Ed. If Cole files her 2019 return, she’ll also receive $1,700.
Unanswered question: We don’t know if the IRS will deny the dependent credit to Cole if Jett received the refund for that dependent already.