(a) In addition to the penalty imposed by Section 19706, if any “S” corporation required to file a return under Section 18601 for any taxable year fails to file the return at the time prescribed therefor (determined with regard to any extension of time for filing), or files a return that fails to show the information required under Section 18601, then that “S” corporation shall be liable for a penalty determined under subdivision (b) for each month (or fraction thereof) during which that failure continues (but not to exceed 12 months), unless that failure is due to reasonable cause.

(b) (1) For purposes of subdivision (a), the amount determined under this subdivision for any month is the product of the following:

(2) Eighteen dollars ($18), multiplied by the number of persons who were shareholders in the “S” corporation during any part of the taxable year.

(c) The penalty imposed by subdivision (a) shall be assessed against the “S” corporation.