Rev. & Tax. Code, § 18601

(a) Except as provided in subdivision (b), (c), or (d), every taxpayer subject to the tax imposed by Part 11 (commencing with Section 23001) shall, on or before the 15th day of the fourth month following the close of its taxable year, transmit to the Franchise Tax Board a return in a form prescribed by it, specifying for the taxable year, all the facts as it may by rule, or otherwise, require in order to carry out this part. A tax return, disclosing net income for any taxable year, filed pursuant to Chapter 2 (commencing with Section 23101) or Chapter 3 (commencing with Section 23501) of Part 11 shall be deemed filed pursuant to the proper chapter of Part 11 for the same taxable period, if the chapter under which the return is filed is determined erroneous.

(b) In the case of cooperative associations described in Section 24404, returns shall be filed on or before the 15th day of the ninth month following the close of its taxable year.

(c) In the case of taxpayers required to file a return for a short period under Section 24634, the due date for the short period return shall be the same as the due date of the federal tax return that includes the net income of the taxpayer for that short period, or the due date specified in subdivision (a) if no federal return is required to be filed that would include the net income for that short period.

(d) (1) In the case of an “S corporation” described in Section 1361 of the Internal Revenue Code, relating to S corporation defined, returns shall be filed on or before the 15th day of the third month following the close of its taxable year.

(2) For taxable years beginning on or after January 1, 1997, each “S corporation” required to file a return under subdivision (a) for any taxable year shall, on or before the day on which the return for the taxable year was filed, furnish each person who is a shareholder at any time during the taxable year a copy of the information shown on the return.

(e) For taxable years beginning on or after January 1, 1997:

(1) A shareholder of an “S corporation” shall, on the shareholder’s return, treat a Subchapter S item in a manner that is consistent with the treatment of the item on the corporate return.

(2) (A) In the case of any Subchapter S item, paragraph (1) shall not apply to that item if both of the following occur:

(i) Either of the following occurs:

(I) The corporation has filed a return, but the shareholder’s treatment of the item on the shareholder’s return is, or may be, inconsistent with the treatment of the item on the corporate return.

(II) The corporation has not filed a return.

(ii) The shareholder files with the Franchise Tax Board a statement identifying the inconsistency.

(B) A shareholder shall be treated as having complied with clause (ii) of subparagraph (A) with respect to a Subchapter S item if the shareholder does both of the following:

(i) Demonstrates to the satisfaction of the Franchise Tax Board that the treatment of the Subchapter S item on the shareholder’s return is consistent with the treatment of the item on the schedule furnished to the shareholder by the corporation.

(ii) Elects to have this paragraph apply with respect to that item.

(3) In any case described in subclause (I) of clause (i) of subparagraph (A) of paragraph (2), and in which the shareholder does not comply with clause (ii) of subparagraph (A) of paragraph (2), any adjustment required to make the treatment of the items by the shareholder consistent with the treatment of the items on the corporate return shall be treated as arising out of a mathematical error and assessed and collected under Section 19051.

(4) For purposes of this subdivision, “Subchapter S item” means any item of an “S corporation” to the extent provided by regulations that, for purposes of Part 10 (commencing with Section 17001) or this part, the item is more appropriately determined at the corporation level than at the shareholder level.

(5) The penalties imposed under Article 7 (commencing with Section 19131) of Chapter 4 shall apply in the case of a shareholder’s negligence in connection with, or disregard of, the requirements of this section.

(f) The amendments made to this section by the act adding this subdivision shall apply to returns for taxable years beginning on or after January 1, 2016.