How to receive the Invoice unique identifier

Hello Team,

We use the following endpoint to receive Invoices - http://{BASE_URL}/Sage300WebApi/v1.0/-/SAMLTD/AR/ARInvoiceBatches

But, Sage 300 API doesn't return the Invoice unique identifier.

Invoice Batch is not unique due to combining a few invoices.
The invoice document number doesn't unique too, because the user can change the Invoice number on UI.
Could you recommend what field we can consider as the Invoice unique identifier?