Which statement is correct for external number assignment during manual posting?

In the context of external number assignment during manual posting in SAP, the process allows users to manually define the document number they wish to use. This flexibility is particularly useful for organizations that have specific numbering conventions or requirements for their documents, such as invoices or payment receipts.

When a user is manually posting a document and opts for external number assignment, they need to input the document number themselves. This approach ensures that the user has complete control over the numbering process, allowing for entries that align with historical records or organizational practices.

The other options do not accurately reflect the nature of external number assignment. For instance, stating that the number is the last document number or that it must be assigned in a sequence contradicts the manual aspect of this method, as it doesn't allow for user discretion. Automatic assignment would imply the system generates the number, which is not the case when external assignment is chosen. Thus, the correct answer highlights the user-centric aspect of this process.