Congress built a speed limit into one of Medicare’s most closely watched annual numbers. The Centers for Medicare & Medicaid Services says the Part D base beneficiary premium, the reference figure insurers use in pricing stand-alone drug plans, cannot grow by more than 6% in any year from 2024 through 2029. For 2027, that base premium comes in at $41.33, up from a lower figure the year before but still bound by the same annual ceiling.
What the 6% cap doesn’t limit: The cap slows how fast the base premium can climb through 2029, not what a specific plan’s premium, deductible or out-of-pocket costs will be next year. The Medicare Cost & Coverage Protection Kit tracks those separately. Track drug costs against the new out-of-pocket cap →
The 6 Percent Cap, Explained
CMS’s Medicare Part D 2027 bid information fact sheet confirms the base beneficiary premium is capped at growth of no more than 6 percent a year for 2024 through 2029, under the premium stabilization provision Congress added to Part D. For 2027, the fact sheet puts the base premium at $41.33 and the related national average monthly bid amount, the figure plans use in calculating that premium, at $296.05.
What the Base Premium Actually Sets
The base beneficiary premium is not a bill anyone pays directly; it works more like a benchmark. Medicare’s guidance on the cost of Medicare drug coverage shows that same base figure doing double duty as the foundation for the late enrollment penalty, which adds 1 percent of the base premium for every month someone went without Part D or other qualifying drug coverage after becoming eligible for it. In 2026, that base figure used for the penalty calculation was $38.99, a separate number from the $41.33 base beneficiary premium set for 2027, since the penalty formula for a given year uses whichever base amount applies at the time the penalty is assessed. Because the 6 percent cap slows how fast the base premium itself can rise, it indirectly slows how fast that penalty calculation can grow too, even for someone who has never been late signing up in the first place.
The Demonstration That’s Ending
The 6 percent cap has been operating alongside a separate, temporary program: a Part D premium stabilization demonstration that ran through 2025 and 2026 to soften premium swings during the drug benefit’s redesign. CMS’s fact sheet says that demonstration is discontinued at the end of calendar year 2026, meaning 2027 pricing reflects standard market conditions for the first time since the redesign began, with the statutory 6 percent cap left as the one ceiling still in place on the base premium going forward.
Two Different Numbers Moving the Other Way
The base premium’s 6 percent ceiling has no bearing on two other Part D figures that are both going up for 2027. Medicare’s page on drug coverage costs lists the maximum deductible a plan can charge rising from $615 to $700, and the annual out-of-pocket cap rising from $2,100 to $2,400. Those figures describe what a person pays out of pocket before catastrophic coverage takes over, a separate question from what an insurer charges for the premium itself, and neither one is subject to the 6 percent limit that applies to the base premium alone. A plan whose own premium sits well above the base figure can still raise that premium by more than 6 percent in a given year, since the statutory cap governs only the national reference number CMS publishes, not any individual insurer’s pricing decision.
A Cap With an End Date
The 6 percent ceiling is written into law for a specific stretch of years, 2024 through 2029, not as a permanent feature of how Part D premiums are set. CMS’s fact sheet frames the cap as part of the broader Part D redesign that also reshaped the deductible and the annual out-of-pocket limit, and it does not address what governs premium growth once 2029 ends, since that question sits outside the scope of a fact sheet written for the 2027 plan year. For now, every year through 2029 carries the same 6 percent limit on the base beneficiary premium, regardless of how sharply drug costs or plan bids move underneath it.
The Same Cap for Either Way of Getting Part D
Medicare’s drug coverage basics page describes two paths into Part D coverage: a stand-alone drug plan, or drug coverage bundled into a Medicare Advantage plan that includes drug benefits. The base beneficiary premium and its 6 percent cap apply to the reference figure used in pricing stand-alone plans, and an individual plan’s actual premium can land above or below that base depending on the insurer and the plan, though the underlying benchmark itself cannot swing further than 6 percent in a single year through 2029 no matter which path a person takes. Someone comparing a stand-alone plan against a Medicare Advantage plan with drug coverage bundled in is still comparing two different premiums built on two different pricing structures, even though both trace back to the same capped national figure somewhere in their calculation.
Where the 6% Cap Doesn’t Reach
The 6 percent annual cap on the base beneficiary premium limits how fast that one reference figure can grow through 2029, but it says nothing about the deductible, the out-of-pocket cap or what a specific stand-alone plan actually charges for the drugs someone takes. Those numbers move on their own schedule even while the base premium’s growth stays capped.
The Medicare Cost & Coverage Protection Kit tracks the new Part D out-of-pocket cap alongside a medication and cost tracker, so a rising drug bill can be checked against what changed for 2027 and what didn’t.
Track the new out-of-pocket cap against an actual medication list in The Medicare Cost & Coverage Protection Kit.
This article was produced with AI assistance and reviewed by a human editor before it was published.
