IRS to Handle Unemployment Returns, Don't Amend
You should not amend your 2020 federal tax return if your original return included unemployment benefits and was filed before the passing of the $10,200 exclusion. The IRS has indicated it will refigure taxes on these returns and adjust the taxpayer's account accordingly. The IRS will then send any refund amount directly to the taxpayer.
The IRS has not yet communicated a timeline for making adjustments and sending refunds.
We will be looking for an official news release in the coming days at https://www.irs.gov/newsroom.
If your state return conforms to the federal unemployment exclusion, you may still need to file amended state returns.