Opinions vary:
"Ex" received the first stimulus, and will likely get the $600 going out early now too. IF the Ex, does receive the second stimulus for that dependent, the Ex should properly give the $600 to the current custodial parent...but that's between them.
Perhaps the IRS is tracking SS numbers (Hope so) , and thus on the 2020 tax return, the Custodial spouse might get neither stimulus, even if he/she declares it was not received for that dependent on the tax form. Then a supposed refund might be reduced by the IRS such that both stimulus amounts, and a refund could even turn into an unexpected "balance due".
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
