In other words, your total out-of pocket drug spending (TrOOP) moves with you when you move to another Medicare Part D plan.
If you move to another Part D plan with a different Medicare Part D plan design - for example, assume your old Part D plan had an initial deductible and your new Part D plan does not have an initial deductible - your previous drug spending will determine where you are within the phases of your new Medicare Part D plan.
If you had retail drug costs that exceeded your out-of-pocket threshold or RxMOOP ($2,000 in 2025 and $2,100 in 2026) and were in your previous Medicare Part D plan's Catastrophic Coverage phase - you will remain in Catastrophic Coverage for the remainder of the plan year.
Review: Medicare notes that,
"[t]rue out-of-pocket (TrOOP) costs are the expenses that count toward a person’s Medicare drug plan out-of-pocket threshold of [($2,000 in 2025 and $2,100 in 2026). Read more about changes in 2025]. TrOOP costs determine when a person’s catastrophic coverage will begin." [links and annual values added]
More from the Centers for Medicare and Medicaid Services (CMS)...
"Part D rules [42 CFR §423.104(d)] require sponsors to track the beneficiary’s TrOOP and correctly apply these costs to the TrOOP limit in order to provide enrollees the catastrophic level of coverage at the appropriate time. The TrOOP threshold is calculated on an annual basis and must be transferred between Part D sponsors if a beneficiary disenrolls and re-enrolls at any time before the end of a coverage year or whenever a Part D plan other than the plan of record has paid. Sponsor collection, and transfer if appropriate, of the TrOOP and gross covered drug spending balances are essential for sponsors to correctly manage the Part D benefit.". (page 36) [emphasis added]Medicare Prescription Drug Benefit Manual, Chapter 14 - Coordination of Benefits, (Rev. 18, 09-17-18), Section 50.8 – Transferring TrOOP Balance When a Beneficiary Changes Part D Sponsors (Rev. 17, Issued: 08-23-13, Effective Date: 06-07-10, Implementation Date: 01-01-11), (https://www.cms.gov/ medicare/coverage/ prescription-drug-coverage-contracting/ prescription-drug-benefit-manual) * Gross covered drug costs (GCDC) amount to the retail value of the formulary medications you purchase or "the total cost of drugs (including dispensing fee and sales tax) regardless of payer" and include "certain dispensing fees, but not including administrative costs." The beneficiary’s accumulated gross covered drug costs determine" whether the "beneficiary is in the Deductible or the Initial Coverage Phase".
Related Questions:
If I change my Medicare prescription drug plan during the year, will my drug deductible transfer to the new Part D plan?
If I change Medicare Advantage plans during the year, will the amount that I have already spent out-of-pocket for Medicare Part A and Part B coverage transfer to the MOOP of my new plan?
Additional Sources
PDE Manual p. 9-18, https://oig.hhs.gov/oei/ reports/oei-05-07-00610.pdf, and 42 CFR 423.308)
Medicare Prescription Drug Benefit Manual, Chapter 14 - Coordination of Benefits, (Rev. 18, 09-17-18)
(https://www.cms.gov/ medicare/coverage/ prescription-drug-coverage-contracting/ prescription-drug-benefit-manual)