Revenue and Taxation Code § 6904

(a) Every claim shall be in writing and shall state the specific grounds upon which the claim is founded.

(b) A claim filed for or on behalf of a class of taxpayers shall do all of the following:

(1) Be accompanied by written authorization from each taxpayer sought to be included in the class.

(2) Be signed by each taxpayer or taxpayer’s authorized representative.

(3) State the specific grounds on which the claim is founded.