If you retired due to a disability, the pension you receive through an employer-paid plan counts as wage income until you reach the minimum retirement age (the age at which you can receive a pension if not disabled). Once you reach that minimum retirement age, the pension is no longer reported as wage income but as pension income.
To find the minimum retirement age for your plan, read the plan agreement or ask the plan administrator. Also, per the IRS, "Minimum retirement age generally is the age at which you can first receive a pension or annuity if you aren't disabled."
For more information, please see this IRS link: https://www.irs.gov/publications/p575/ar02.html