How the plan spreads Part D drug costs into monthly bills under the $2,100 cap
Updated October 2026
The Medicare Prescription Payment Plan, created by the Inflation Reduction Act and available since 2025, lets anyone with a Part D plan or a Medicare Advantage plan with drug coverage pay out-of-pocket drug costs in monthly installments instead of at the pharmacy counter. You pay $0 at the pharmacy for covered drugs; the plan sends a bill each month. There is no interest and no fee. It does not lower what you owe: total payments equal your out-of-pocket costs, which are capped at $2,100 for 2026.
First month in the plan: bill = the lesser of that month’s out-of-pocket costs and the maximum possible payment, which is (annual cap − out-of-pocket costs already paid this year) ÷ months left in the year. Each later month: bill = (unbilled balance + new costs that month) ÷ months left. Once your costs reach the cap, new prescriptions cost $0 and the bills just spread what is left.
January: maximum possible payment $2,100 ÷ 12 = $175.00, less than $525, so the bill is $175.00 and $350 carries over. February: ($350 + $525) ÷ 11 = $79.55. March: ($795.45 + $525) ÷ 10 = $132.05. April: ($1,188.40 + $525) ÷ 9 = $190.38, and the $2,100 cap is reached. May through December: the remaining balance divided by the months left, $190.38 a month.
| Month | Drug costs at the pharmacy | Plan bill |
|---|---|---|
| January | $525.00 | $175.00 |
| February | $525.00 | $79.55 |
| March | $525.00 | $132.05 |
| April | $525.00 | $190.38 |
| May | $0.00 | $190.38 |
| June | $0.00 | $190.38 |
| July | $0.00 | $190.38 |
| August | $0.00 | $190.38 |
| September | $0.00 | $190.38 |
| October | $0.00 | $190.37 |
| November | $0.00 | $190.38 |
| December | $0.00 | $190.37 |
Medicare.gov’s table repeats $190.38 for December; this calculator settles the exact remaining balance in the last month ($190.36), so the year adds up to exactly $2,100.
The plan helps most when large costs come early in the year: a $2,100 fill in January becomes twelve $175 bills. With steady, modest costs it can make things worse: in Medicare.gov’s $80-a-month example, bills start at $80 and $7.27 and climb to over $240 by December, because each month’s costs are pushed later. CMS describes people likely to benefit as those with high costs early in the plan year; plans and pharmacies are required to tell people identified as likely to benefit.
| Situation | First bill | Highest bill | Total billed |
|---|---|---|---|
| $525 a month, joined January (Medicare.gov example 1) | $175.00 | $190.38 | $2,100.00 |
| $80 a month, joined January (Medicare.gov example 2) | $80.00 | $241.59 | $960.00 |
| One $2,100 fill in January | $175.00 | $175.00 | $2,100.00 |
| $300 a month, joined July | $50.00 | $50.00 | $300.00 |
| $525 a month in 2027 ($2,400 cap) | $200.00 | $225.61 | $2,400.00 |
Joining in July spreads costs over only six months, so bills are higher; costs paid before joining count toward the cap and are subtracted from it.
The annual out-of-pocket maximum for covered Part D drugs is $2,100 in 2026 and $2,400 in 2027, according to Medicare.gov. The cap rises each year with Part D costs. Because the first-month limit is the cap divided by months left, the 2027 January limit for a full year is $200.
Enter your expected out-of-pocket cost per month for covered drugs (your copays and coinsurance, from your plan’s drug list or recent pharmacy receipts), the month you join, and any one-time costs, such as a new prescription, as month:amount pairs, for example 4:613. Costs in months before you join are treated as paid at the pharmacy and reduce the cap left to spread. Plan premiums are not part of the payment plan.
You can opt in before or during the year through your plan, and leave at any time; any balance you owe is then billed on the plan’s schedule. If you miss a payment, the plan must give a grace period of at least two months before it can remove you, and it can require you to pay what you owe before rejoining the next year. People with Extra Help already have low copays and usually gain little from the plan.
It assumes the same cost every month plus the one-time costs you list, and that all of them are covered Part D drugs. It does not model your plan’s deductible phase separately (it is already inside your out-of-pocket costs), drugs not covered by your plan, premiums, or how a plan rounds individual bills. Your plan’s monthly statement is the official bill. A SHIP counselor or your plan can help you decide whether to opt in.
Thinking it lowers costs. It changes only timing. Joining for small, steady costs and getting larger bills late in the year. Not checking whether your election carries into next year; ask your plan before January. Paying the pharmacy anyway: once enrolled, covered drugs should cost $0 at the counter. Assuming premiums are included; they are billed separately.