They sit on different layers: one governs assets, the other governs actions
A Business Manager, now often called a business portfolio in Meta's interface, is a container. Ad accounts, Pages and pixels or datasets are the assets inside it. Roles at the BM level decide who can manage the container: add or remove people, assign assets and edit business settings. Permissions on an ad account only decide what someone can do inside that single account, such as viewing results, creating and editing ads or changing account settings. Being able to run ads is therefore not the same as controlling the account. Someone can have full operating access and still have no say over which BM the account belongs to.
Ownership is singular: the ad account belongs to the BM that created or claimed it
At any time an ad account has one owning BM. Other BMs can only get access as partners. A partner can run ads but does not own the account, and the owning BM's admins can revoke the share whenever they want. In general, an ad account already owned by one BM cannot simply be moved to another, only shared. Check Meta's current help pages for the exact limits. The practical test for long-term control is whether you are a full-control person on the owning BM, not what your role inside the ad account is called.
Payment and billing fields are usually a second gate
Payment methods, billing details and spending limits often do not come bundled with ordinary advertising permissions. Business settings include separate finance-related roles for viewing or editing payment information and invoices. A common pattern is that an operator can build ads and change budgets but cannot touch the payment method. Who owns the card or payment entity also matters when charges are disputed or an account is restricted, because it affects who can appeal and resolve it. Before taking over or sharing an account, confirm three things separately: whose name the payment method is under, who can edit it, and which email receives billing notices.
The ability to remove people shows who really holds control
The most direct way to judge control is to ask who can remove others. A full-control person on the BM can manage all members and asset assignments, including pulling another person's ad account access. A member with only ad account access usually cannot do that, and certainly cannot remove the BM's own admin. If a BM has just one admin, that person's account being restricted, locked out or departing leaves the whole BM and its ad accounts with nobody able to manage them. A safer setup keeps at least two trusted full-control people and turns on two-factor authentication for every admin account.
Checklist before taking over or sharing an account, and when to stop
Check each item: which BM owns the ad account and what level your login holds there; whether the account has restrictions or unpaid balances; whose payment method is attached and whether you can replace it; whether other BMs retain partner access; and whether business verification matches the real entity. If the other side will only grant ad account level access and will not put you on the owning BM's admin list, you are getting use rights, not control. Treat it as temporary and do not build long-term assets on it. If they cannot explain ownership or the payment entity, pause the deal.