Billing integrity is the accuracy and reliability of charges, purchases, refunds, and account credit inside a payment system. It means the service records usage and payment state correctly, so a user is billed once, credited once, and granted the right entitlement for what was actually paid for.
In cyber security, billing integrity matters because payment flows are a trust boundary. Attackers may try to tamper with client-side purchase data, replay payment confirmations, abuse refunds, or use stolen credentials to spend credit fraudulently. Defenses usually rely on server-side entitlement checks, signed or tokenized payment events, idempotent transaction handling, and audit logs that let providers reconcile usage against payments. In metered services such as cloud gaming, billing integrity helps ensure that time limits, paid hours, and account balances stay consistent across the billing system and the access control layer.