How do I check the status of an amendment?

When did you mail it?  Or did you efile it after Aug 17?

In normal times it takes up to 16 weeks or more to process an Amended 1040X return.  But these are not normal times.

Sorry the IRS has limited staff due to Covid-19.  They started opening the mail in June that's been stacking up. Back in March the IRS closed their processing centers and stopped processing mailed tax returns.  An IRS spokesperson said that they have about 11 million pieces of unopened mail.  The IRS says....."We’re experiencing delays in processing paper tax returns due to limited staffing. If you already filed a paper return, we will process it in the order we received it."  So it may take longer if you mailed in June or later.   So you have to keep waiting.

See this IRS page for the latest information

https://www.irs.gov/newsroom/irs-operations-during-covid-19-mission-critical-functions-continue

Then once they start opening the mail, After 3 weeks you can track it here,    

https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1