Whether or not it's tax free depends on who paid the premiums and whether it was with pre-tax or post-tax dollars. If you paid all of your premiums, then it is tax free. However, if your employer paid for the premiums or you paid with pre-tax dollars, it is 100% taxable.

This is regarding a disability policy and in no way do I speak in regards to State Disability, SSD or any other type of disability for which I claim no knowledge outside of what I have personal experience with.