How to avoid duplicate lease invoices

Summary: We currently have vendors creating invoices for leases manually. We're working on migrating into the lease module where invoices will be automatically generated. In a perfect world, we would have vendors trained to stop doing manual invoices on day one, but of course that would be highly challenging. Are there tools in the system to prevent this? I tried to manually create a duplicate invoice in our test system and didn't get any duplicate error.

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