Why do you think you have to "prove" that you have health insurance? Where are you being asked for proof? You only have to enter information about health insurance if you have a 1095A for health insurance from the marketplace ("Obamacare") You do not enter a 1095B or a 1095C anywhere. As for Medicare.....if you are getting Social Security, when you enter your SSA1099, the Medicare premiums you are paying from your SS benefits are flowing automatically to medical expenses.