The hold harmless rule is intended to prevent a person’s Social Security benefits from declining from one year to the next. This otherwise would happen if annual increases in Medicare Part B premium are larger than annual cost of living increases (COLA) in Social Security.
The hold harmless rule applies to any Social Security benefit – retirement, spousal, survivor, etc. — from which Medicare premiums are deducted. Remember that Part B premiums must, by law, be deducted from a person’s Social Security payments if the person has claimed a benefit.
A person who applies for Medicare cannot be held harmless in the year they get Medicare, only in subsequent years.
A Medicare enrollee who has not yet claimed Social Security benefits would pay Part B premiums directly to Medicare every three months. People who pay their premiums directly to Medicare are not held harmless from future Part B increases.
Applying for Social Security benefits will never increase your Part B premiums, and could protect you from future increases should rates of inflation again fall to low levels and result in cost of living adjustments in Social Security that are too small to cover annual increases in Part B premiums.