You generally do not need to amend for Federal.

However, taxpayers would have to file an amended return if they did not originally claim the EITC or other credits, but now are eligible because the [unemployment comp] exclusion changed their income.  These taxpayers may want to review their state tax returns as well.

IRS to recalculate taxes on unemployment benefits; refunds to start in May | Internal Revenue Servic...

See these re State:

How is my state taxing unemployment income? (intuit.com)

Do I need to amend my state return to update my un... (intuit.com)

If you are asking if there is any additional charge for amending the tax return, the answer would be No.  There is no charge for amendment.  

If you have already filed, you do not need to amend.  The IRS will re-calculate your taxes and send you the refund.  For details from the IRS, click here:  No amendment

Per IRS, "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."

@sandra-2020