§ 19. Filing of documents with the retirement system. Whenever a statute requires that a document be filed with the state comptroller, as administrative head of the New York state employees' retirement system, within a prescribed period of time or by a specified date, and such document has been mailed to the comptroller or the retirement system by United States Postal Service certified mail, return receipt requested, the document shall be deemed filed on the date of mailing. Notwithstanding this provision, no document shall be deemed filed on the date of mailing unless it is actually received by the retirement system as a result of such mailing.