William™ by Certifi is purpose-built premium billing and payment software for health plans and health insurers. Unlike billing modules bundled into core admin platforms, William™ is designed from the ground up to handle the complexity of health plan billing — including ACA marketplace, Medicare Advantage, Medicaid, and commercial lines of business. Built on the Perfect Balance™ accounting architecture, William™ enforces balanced debits and credits at every transaction, virtually eliminating the manual reconciliation work that plagues teams using legacy or core admin billing systems. Key capabilities include: Automated invoice generation, retroactive adjustments, and payment matching Integrated member payment portal (ACH, credit/debit card, retail cash) Configurable delinquency management with automated letter generation Real-time billing data via API for member portals and service teams No-code billing rule configuration — no developer required Integration with upstream enrollment platforms and downstream GL systems via API, flat file, or SSO William™ is PCI, NACHA, SOC2, and HIPAA compliant and is designed to scale to millions of transactions per month.