Account
An Account is the financial bucket that aggregates every transaction made against a patient within a facility. You touch it indirectly: charge items land on a patient's default account, and invoices and reconciliations settle against it.
Charge Item
A ChargeItem is a single billable line for a service or product supplied to a patient — what was charged, the quantity, the unit and total price components, and any discounts or override reasons. You create one against a patient (and optionally an encounter); it always settles onto an Account.
Invoice
An Invoice groups charge items raised against a single account into one billable document, with snapshotted line items, totals, and a lifecycle status. You touch it whenever you bill a patient, issue a refund, or reconcile payments.
Payment Reconciliation
A PaymentReconciliation is a single payment recorded against an Account, and optionally allocated to one Invoice. It captures how much was paid, by what method, when, and by whom — mirroring the FHIR PaymentReconciliation resource. Reach for it whenever you post a payment, refund, credit note, or adjustment to a patient or insurer account.