CGOCORE013 (BILLING_INVOICE_EFFECTIVE_DATE)

You can use this setting to determine the tariff effective date when you generate an invoice using the Generate Invoice form.

EVENT_PERFORMED_DATE (default) - Use the tariff based on the event performed date.

CONTRACT EFFECTIVE DATE - Use the tariff based on the contract effective date.

By default, N4 Billing applies the Use tariff on event performed date option while generating invoices.