All employee compensation is subject to tax unless the tax code specifically excludes it. That's the case for certain employer-provided benefits.
The most tax-costly company perk is health care. The value of what your employer pays for worker medical insurance premiums, long-term care coverage and health care doesn't cost you a tax cent.
But it does cost Uncle Sam. Through 2018, employer-provided health care benefits will keep the U.S. Treasury from getting its hands on some $785 billion.