Don't know when. The IRS doesn't have a way to look that up. If you have filed early before the exclusion, the IRS will recalculate your return for the new 10,200 unemployment exemption for you. There is no need for taxpayers to file an amended return unless the calculations make the taxpayer newly eligible for additional federal credits and deductions not already included on the original tax return.
See IRS article May 14, 2021
https://www.irs.gov/newsroom/irs-begins-correcting-tax-returns-for-unemployment-compensation-income-...
