Self employed
Medical insurance premiums, including Medicare, may be allowable as self-employed health insurance deductions if you are self-employed. The main requirement is that you can't be eligible to participate in a subsidized employer health insurance plan, either through your or your spouse's employer. You can learn more in this Intuit article. The deduction is from your income for income tax purposes, it is not a deduction on your business income and expense Schedule C, but you will enter the premiums in that self-employed section when you enter your business expenses:
