Using the Resequencing Feature:

Go to general settings > Scroll down > activate developer mode. 

Then go to an existing invoice.

Click Action > Resequence.

This will regenerate the invoice number based on the updated prefix and sequence settings.

To ensure invoice numbers update correctly in the desired format (e.g., INV202412001), it's important to use separators like / or - between parts of the sequence. For example, use INV/2024/12/001 or INV-2024-12-001.

Without these separators, the system can't tell the difference between the year, month, and sequence, and it won’t reset the sequence when a new month starts. The separators help the system identify each part and automatically resequence invoices correctly.