According to the instructions at https://www.ftb.ca.gov/forms/2012/12_3522.pdf
"Enter all the information requested using black or blue ink. To ensure the timely and proper application of the payment to the LLC's account, enter the SOS file number (assigned upon registration with the SOS), and the federal employer identification number (FEIN)."
Based on that the EIN is generally preferred over the SSN.
It is very important that the number used is consistent both year to year and with prior filings with the state of California. This will assure proper application of the payment to the LLC's account.
You may also wish to consider using the online Web Pay for Businesses.
After a one-time online registration, businesses can make an immediate payment or schedule payments up to a year in advance. For more information, go to https://www.ftb.ca.gov/online/WebPay/Business_Entities.asp
Please ask if you need clarification.
Well of course I read that same information but I understood that single-member LLCs are an exception and should normally use their SSN not their EIN for tax purposes since a single-member LLC is a "disregarded entity" for tax purposes. Unfortunately this form does not include a space for an SSN number.
While it is true that for federal reporting (except payroll) that an LLC uses the Social Security number that is not true for state reporting.
The LLC is a state created entity that is basically not recognized by the federal government and especially so with the single member LLC that is a disregarded entity.
That is why there are differences between the state and federal reporting.
So, you are correct about using your SSN for federal tax but the state wants you to use an EIN.
Please ask if you need more discussion.