Which Revision To Use Use the July 2021 revision of Form 1040-X to amend 2019 and later tax returns, until a later revision is issued. Use these instructions with the July 2021 revision of Form 1040-X. If you are amending a 2018 or earlier tax return, use the prior revision of this form and instructions both dated January 2020. All revisions are available at
Just curious, why are you filing older returns. You can't claim refund over 3 years. If you are filing because of irs letter you should call number on letter and ask that question.