Do you have this bookmarked?

https://gpwcpas.com/grant-credit-loan-and-other-relief-comparison-chart/

Although it has been updated for the recent SB change, they forgot to change the date at the top. That's the biggest issue right now, when using web resources, because so mane changes are happening so fast, and what you read might be superseded while you are reading it (ha ha ha).

ERC for CA: "The refund is taxable for California and the expenses are deductible."

So I don't know that you need to amend anything. Just report the refund as business income when the banking happens, for a cash basis entity. An accrual basis entity would have accrued the refund. If you got it as a credit, you were allowed to retain amounts collected from employees as advance payment for the employer tax credit.