Sole proprietors filing a Schedule C attached to Form 1040 can include all premiums paid for all parts of Medicare for the self-employed health insurance deduction on the from page of the 1040 form.  This includes medicare premiums paid on behalf of the self-employed's spouse.

Partners can also use this deduction as long as the partnership pays the premiums directly or reimburses the partner AND includes them in guaranteed payments to the partner on the partner's K-1. 

Finally, an S Corporation owner-employee can use this deduction if the company pays the premiums directly or reimburses the shareholder AND includes those payments as taxable income in the shareholder employee's W-2.

If you qualified but missed this tax deduction in any open tax year, you can amend and file for a refund.