California Code, Unemployment Insurance Code - UIC § 1132

Except in the case of failure without good cause to file a return or report, fraud or intent to evade any provision of this division or authorized regulations, every notice of assessment shall be made within three years after the last day of the month following the close of the calendar quarter during which the contribution liability included in the assessment accrued or within three years after the deficient return or report is filed, or was due, whichever period expires the later.  An employing unit may waive this limitation period or may consent to its extension.

In case of failure without good cause to file a return or report, every notice of assessment shall be made within eight years after the last day of the month following the close of the calendar quarter during which the contribution liability included in the assessment accrued.  An employing unit may waive this limitation period or may consent to its extension.