[en] A Guaranteed Shutdown State (GSS) for a CANDU reactor is one in which the reactor will remain in a stable sub-critical state independent of reactivity perturbations caused by any possible changes in core configuration, core properties or process system failures. The usual procedure incorporated in the CANDU reactor design and specified in the operating procedures for entry into GSS is to over-poison the moderator (typically with Gadolinium nitrate solution). An additional guaranteed shutdown state for the currently in operation CANDU reactors, Rod-Based Guaranteed Shutdown State (RBGSS), using all solid rods, i.e., SDS1, MCA and adjusters, has been proposed and implemented at Pickering and Darlington reactors. The CANDU reactor designer has also considered this option and included it as a new feature in the Enhanced CANDU-6 design. The paper discusses the regulatory requirements for GSS and CNSC staff expectations related to information in support of an application for regulatory approval of RBGSS as an additional GSS in existing CANDU reactors. (authors)