Chapter 9, Part V of the Patent Examination Guide 2.2.2 Termination
If the annual patent fee is not paid or the annual patent fee or late payment fee is not paid in full, the examiner shall issue a notice of patent termination two months after the expiration of the annual patent fee. If the patentee fails to start the recovery procedure or the request for recovery of the right is not approved, the Patent Office shall declare it invalid within four months after the termination notice is issued, and make an announcement in the patent bulletin.