There is a box on my form W2 that has the amount that my employer paid for my health insurance last year. That is my proof. I already e-filed my federal tax return. It is only a matter of time before the feds start taxing the employer paid health insurance. Assuming a marginal tax rate of over 30% that will be a substantial bite.
The biggest mistake ever made in health care was tying it to employment (WW2 era). Once you have one entity paying and another consuming, costs by definition will skyrocket.