Billing that reads from the agreement.
Most billing systems store a plan and a price and infer the rest. That holds until someone upgrades mid-term, adds seats in week three, or renegotiates at renewal — and then the invoice and the agreement start disagreeing. Here the billing schedule is derived from the contract, so they cannot.
What it handles
The unglamorous cases, which are the ones that actually come up.
Proration and mid-term change — Upgrades, downgrades and quantity changes are prorated against the terms in force on the day they happen, not against whatever the plan says today.
Per seat and usage — Seat counts that move during a period, and usage components metered and rated alongside the fixed ones on the same invoice.
Trials, credits and one-offs — Trial periods, granted credit and one-time charges sit on the same subscription rather than in a spreadsheet beside it.
Retries and dunning — Failed payments retried on a schedule, then escalated — on cards and on invoices alike, since an unpaid invoice needs chasing as much as a declined card.
Renewals, pauses and cancellation — Each one a recorded transition on the contract, including cancellation at period end, so the billing schedule and the agreement never drift apart.
The same engine in both modes
None of this depends on who the seller of record is. In Managed the documents are issued under Lernaura; in Direct they are issued under your own entity, and the registrations and returns stay yours. The billing logic, the proration and the records are identical either way.
Where it sits
Billing is one link in a longer chain — the contract at one end and audited revenue at the other.