California Revenue & Taxation Code
Cal. Rev. & Tax. Code § 19308
The period within which a claim for credit or refund may be filed, or credit or refund allowed or made if no claim is filed, shall be the period within which the Franchise Tax Board may mail a notice of proposed deficiency assessment under the same circumstances, if either of the following apply:
# (a)
The taxpayer has, within the period prescribed in Section 19306, agreed in writing, under Article 3 (commencing with Section 19031) of Chapter 4, to extend the time within which the Franchise Tax Board may propose a deficiency assessment.
# (b)
The taxpayer has agreed with the United States Commissioner of Internal Revenue for an extension (or renewals thereof) of the period for proposing and assessing deficiencies in federal income tax for any year.
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