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Invoices are controlled the BILL_ENABLE_INVOICES config options. They are stored in the INVOICES table. Generating Invoices is not dependent on the 'Accounts Receivable' (AR) license.
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Generating Invoices
When the BILL_ENABLE_INVOICES config option is enabled, the Bill process generates INVOICES records. One Invoice is generated for each GLA in the Bill. Invoices are generated with a Pending status. This process creates an incremented Invoice number for each GLA in the Bill. All billing transactions in each Invoice are linked back to the generated Invoice.
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