Well then, I'll guess ACTC.

And what IRS says is:

Taxpayers do not need to file an amended return if they:

• already filed a tax return and did not claim the unemployment exclusion; the IRS will determine the correct taxable amount of unemployment compensation and tax;
• have an adjustment, because of the exclusion, that will result in an increase in any non-refundable or refundable credits reported on the original return; 

https://www.irs.gov/newsroom/irs-readies-nearly-4-million-refunds-for-unemployment-compensation-over...