If you paid the disability insurance premiums with after tax funds, the disability income is not taxable.
Disability income is considered taxable income if the premiums for the disability insurance were paid by your employer, or if you paid for the premiums with pre-tax dollars on your paycheck (If you are not sure, check with your HR department
If you and your employer jointly paid the premiums, only the disability amount covered by your employer's payments are taxable.
See Is disability income taxable?
https://ttlc.intuit.com/questions/1901145-is-disability-income-taxable
