42 C.F.R. § 408.43 Deduction from social security benefits.
Title 42 - Public Health
SSA, acting as CMS's agent, deducts the premiums from the monthly social security benefits if the enrollee is not entitled to railroad retirement benefits. (If the benefit is less than the monthly premium, the benefit is withheld and the enrollee is required to pay the balance through direct remittance.)
Title 42: Public Health
PART 408—PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE
Subpart C—Deduction From Monthly Benefits
§ 408.43 Deduction from social security benefits.

