FA(3) is a structured invoice schema used in Poland to represent invoices in a machine-readable format. Instead of treating an invoice as a free-form document, the schema defines fields for parties, contacts, tax details, line items, dates, and transaction references so different systems can exchange billing data consistently.
From a cyber security perspective, FA(3) matters because structured invoice records concentrate valuable business intelligence in one place. A breached invoice store can reveal supplier relationships, company identifiers, addresses, payment references, and contact details that help attackers craft convincing phishing, vendor impersonation, or invoice-fraud attempts. Defenders treat FA(3)-based data like sensitive business records: restrict access, encrypt data at rest and in transit, validate API requests, log exports, and monitor for unusual bulk access or changes to invoice fields.