rptt rett ucc-1

Hi, everyone. This is my first post, so please be kind. I've recently sent this to the Dept. of Finance: "QUESTION?: Hi,I would like to register a life estate deed on my NYC co-op and could not find the form on your site. Can it be registered online? Thanks for your help" After a one-month delay, I received this cryptic answer: "Cooperative apartments do not have deeds. The only documents you can file for a cooperative is the NYC RPTT AND NYS RETT and the INITIAL COOP UCC 1." Does that mean it can't be done or just that a different set of forms or administrative center applies? I'd appreciate any clarification. Thanks, Rebecca