CA Rev & Tax Code Section 12433

(a)

If before the expiration of the time prescribed in Section 12432 for giving of a notice of deficiency assessment the insurer or surplus line broker has consented in writing to the giving of the notice after that time, the notice may be given at any time prior to the expiration of the time agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon.

(b)

This section shall become operative on July 1, 2013.