it's probably impossible to correctly amend Ca (surprised they have caught it already because the IRS usually informs the state of changes) without amending the Federal by adding the omitted w-2. then you print out the amended Ca forms and mail them with the omitted W-2 and IRS notice
per CA
If the changes made by the IRS result in a refund due, you must file a claim for refund within two years. Use an amended Form 540 and Schedule X to make any changes to your California income tax returns previously filed.
Include a copy of the final federal determination, along with all underlying data and schedules that explain or support the federal adjustment.
