If the proof received, including any medical examination, shows to the satisfaction of the board that the member is permanently incapacitated physically or mentally for the performance of his duties in the service, it shall retire him effective on the expiration date of any leave of absence with compensation to which he shall become entitled under the provisions of Division 4 (commencing with Section 3201) of the Labor Code or effective on the occasion of the member’s consent to retirement prior to the expiration of such leave of absence with compensation. His disability retirement allowance shall be effective as of the date such application is filed with the board, but not

earlier than the day following the last day for which he received regular compensation. Notwithstanding any other provision of this article, the retirement of a member who has been granted or is entitled to sick leave shall not become effective until the expiration of such sick leave with compensation unless the member consents to his retirement at an earlier date.

When it has been demonstrated to the satisfaction of the board that the filing of the member’s application was delayed by administrative oversight or by inability to ascertain the permanency of the member’s incapacity until after the date following the day for which the member last received regular compensation, such date will be deemed to be the date the application was filed.