After you file

Around 3 weeks after the efiled amended return was accepted you can use the tool linked below to start checking the status of the amended return to be sure it was received and is being processed, but it can take up to 3-4 months (or longer in some cases) to fully process.

 

IRS "Where's My Amended Return?"

https://www.irs.gov/filing/wheres-my-amended-return