This bill adds new sections to chapter 74.09 RCW and reenacts and amends RCW 43.84.092. The new health-related sections require the unidentified "authority" and "department" to collaborate so the department notifies the authority when individuals enrolled in both the income-based Medicaid program and other income-based programs have moved out of state, and to consult frontline staff to improve identification. The authority must, by January 1, 2027, have a process to obtain address information from specified reliable sources (examples include returned mail with forwarding address, the USPS national change of address database, managed care organizations when the address is verified by or with the enrollee, and other CMS-approved sources), act on address changes, submit certain identifying information (including Social Security numbers when available and required) and other CMS-requested data to CMS monthly and at each eligibility determination/redetermination beginning no later than October 1, 2029, and determine residency and disenroll individuals who do not reside in the state unless CMS exceptions apply; the authority must adopt rules to implement these requirements. The bill requires the authority to amend managed care contracts and processes to permit recovery of premiums when a managed care enrollee has moved out of Washington and has not received services in the managed care service area, and directs that net recoveries from premiums paid for concurrently enrolled individuals be deposited into a newly created "supporting science, technology, engineering, and mathematics education account" in the state treasury, with moneys available only after appropriation for STEM-related purposes. It also requires the state auditor to conduct a performance audit of concurrent Medicaid enrollments by December 31, 2031. Separately, the bill reenacts and amends RCW 43.84.092 to establish a treasury income account to receive all earnings from investment of surplus treasury balances, to be used for CMIA-related payments and purchased banking services (subject to RCW 43.84.160 and chapter 43.88 RCW), with the Office of Financial Management determining CMIA amounts and directing transfers as needed. The state treasurer must distribute earnings monthly, crediting the general fund except that many named accounts and funds receive proportionate shares based on average daily balances; several chunks list numerous accounts but the complete list is not included here. Some sections have stated effective and expiration dates tied to RCW 74.76.040 and to dates in 2027–2029, but the extracted text does not provide a complete set of effective or contingent expiration dates, and the statutory identities of "the authority" and "the department" are not defined in the provided material.

If enacted, the state will start actively checking whether people enrolled in income‑based Medicaid and related programs have moved out of Washington by using returned mail, the USPS change‑of‑address data, information from managed care plans, and other approved sources, and by consulting caseworkers. The agency in charge must have that address‑checking process in place by January 1, 2027, begin monthly reporting to CMS (including Social Security numbers where required) by October 1, 2029 to help prevent people being enrolled in multiple states, and will likely cancel coverage for people found to no longer reside here. Managed care plans must accept contract changes that let the state recover premiums paid while an enrollee was out of state; recovered net premiums will go into a new STEM education account. These steps are likely to reduce state and plan payments for duplicate out‑of‑state coverage, shift some recovered dollars to STEM program funding, and increase administrative work and recovery risk for managed care organizations and frontline staff. The bill also centralizes all investment earnings from surplus state treasury balances into a new treasury income account that OFM and the state treasurer will use to handle federal CMIA obligations, pay banking service fees, and then distribute remaining earnings monthly to the general fund and a long list of specified accounts in proportion to their average balances. Several sections have set expiration or effective dates tied to RCW 74.76.040, and the text here does not identify exactly which agency is “the authority” or “the department” nor show the full list of recipient accounts, so the precise scope, timing, and long‑term budget effects remain partly unclear.