A one-time $90 payment is going out to 20 million seniors on Medicare this month — small but real money for some, nothing for most beneficiaries.

• The payment is a rebate on Medicare Part B premiums, announced in early October and landing by direct deposit now, with paper checks arriving later in the month.
• To qualify you need original Medicare Part B, you must live in the US, pay the standard premium yourself, and not get Medicaid help with it.
• The biggest excluded group is the 35 million people on Medicare Advantage plans, who get nothing even though they also pay Part B premiums.
• Low-income seniors whose premiums are already covered by Medicaid and high earners who pay extra premiums are both left out.
• The money comes from an existing Medicare fund set up by Congress in 2008, not from new spending — and no application is needed, so anyone calling to ask for bank details is a scammer.

Outlook: Payments finish going out through late October, and critics will keep arguing $90 does nothing about rising health care costs.