“Amounts you receive as workers’ compensation for an occupational sickness or injury are fully exempt from tax if they are paid under a workers’ compensation act or a statute in the nature of a workers’ compensation act. The exemption also applies to your survivors.” IRS Publication, p. 19.
But there are some exceptions that do not apply in most claims:
“The exemption, however, does not apply to retirement plan benefits you receive based on your age, length of service, or prior contributions to the plan, even if you retired because of an occupational sickness or injury. If part of your workers’ compensation reduces your social security or equivalent railroad retirement benefits received, that part is considered social security (or equivalent railroad retirement) benefits and may be taxable.” Id.
As always, talk to your tax professional about your particular situation.
This is a link to the IRS publication 525: