Forget to claim a credit in tax year 2020, plan to send 1040-x to correct it.
By IRS web, " If you need to amend your Form 1040, 1040-SR, 1040-NR, or 1040-SS/PR for the current or two prior tax periods, you can amend these forms electronically using available tax software products"
Does it mean I need file by paper?
