A US green card holder can voluntarily abandon their permanent resident status in the US by mailing the form I-407 and the green card to the USCIS. Then, the USCIS sends the ex-holder a document to acknowledge the receipt and confirm the change of the status.
In what moment does the change of status take place? When the person mails the documents, or when USCIS processes them?
USCIS may take months to acknowledge the abandonment of the green card, so this can have tax implications.