In the case of a deficiency arising under this part during the lifetime of a decedent, a notice of deficiency determination shall be mailed within four months after written request therefor, in the form required by the board, by the fiduciary of the estate or trust or by any other person liable for the tax or any portion thereof.
Source:
Section 6487.1, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=RTC§ionNum=6487.1..