If the Form 1099-R you received for the pension has a code 3 in box 7 (Disability) and you were under the minimum retirement age set by your employer the pension income is reported on Line 1 of the Form 1040.
Go to IRS Form 1040 Instructions for Line 1 on page 24 - https://www.irs.gov/pub/irs-pdf/i1040gi.pdf#page=24
• Disability pensions shown on Form 1099-R if you haven’t reached the minimum retirement age set by your employer
