If you follow the form, it states "Enter the total of all other health insurance premiums paid, which
were not included on 4Y or 4S" (which is: health insurance premiums withheld from your social
security income.) In my case, the only health insurance premiums withheld from my Social Security income are Part B. I pay out of pocket a medical supplement and also a part D prescription premium. I enter the total of those premiums because they are not withheld from my social security and I do not itemize, so they are not deductions as a part of itemization. They are also not reimbursed by any employee retirement benefit, they are totally out of pocket and not deducted anywhere else.
