In November 2021 Boston voters approved a grassroots-led City Charter amendment requiring the Mayor and City Council to establish an Office of Participatory Budgeting by ordinance; the ordinance passed in spring 2023 and requires a nine-member External Oversight Board, an annual review to the Mayor and Council, and a public hearing on funding use and populations served. The ordinance is the Board's only governing document. Within that, the process design is the Office's and Board's own: the Rulebook is adopted and amended by majority Board vote. Bindingness is inferred from rule and practice rather than quoted from the ordinance: the Rulebook says proposals with the most votes are awarded up to the cap, and all winners in both cycles were funded; but proposals pass a City department, Legal and CFO certification before reaching the ballot (one pilot proposal, a non-police construction detail, was removed at that stage), and at the first Board meeting a member's question whether the Mayor could reject a chosen project was answered by describing that pre-ballot filter. The appropriation itself is annual and subject to Mayor and Council approval, with a Special Revenue Fund smoothing balances across years. Scope is full discretion within eligibility rules; ideas are never modified by the City or Board, but proposals are shaped with City staff.