CW 90 days by mail report.
Sent current original slip, copy of documents signed (passport, house registration, departure card) and filled report form by EMS mail 2 weeks before report date
Get confirmation from EMS the envelope was delivered.
Received 90 days slip back today, which is exactly 1 month + 1 day from the report date.
I strongly recommend to send report via EMS to get tracking, signature from receiver and also keep copy of current report in case mail lost for any reason.