A Membership sells tiers with a perks bundle. A Bill sells one content stream, with no tiers and no perks list.
Both are recurring and both give subscribers access to member-only posts. The difference is structural.
Membership
Tiers — bronze through to lifetime, each at its own price, each with its own perks bundle. Up to £100.00 a month.
A Membership cannot be published without at least one on-platform benefit in its perks. Selling access to something that is not here is not a membership to this platform.
Bill
One content stream. No tiers, no perks list. Weekly, monthly or yearly. Up to £100.00 a month.
A Bill has no perks list on purpose. Given one, the two products become indistinguishable and there is no reason to have both.
Which to use
Sell one thing at one price → a Bill. Want to offer several levels of access → a Membership.
Both carry the posting rule
Sell either and you need 3 member posts in a rolling 30 days, or collection pauses. See why have my subscription payments stopped.