Matching customer invoices to multiparty private offers

What’s the best way for a reseller to match an Azure Marketplace customer invoice to its multiparty private offer and subscription in Partner Center? We’ve had invoices missing from our reporting and multiple charges tied to the same offer with different Asset IDs. Which reports or fields should we use to match them?

Can we also see whether a credit was issued, or does that require the customer’s billing access or Microsoft Support?