You should file an amended return with the State of California to claim your refund - you can't count on the IRS or the state to process a refund for you without claiming it. The reason it worked with the IRS is because they thought you owed them money and therefore they contacted you to collect it. When you showed that they actually owed you, they paid up.
If California owes you a refund, you must claim it. They will be perfectly happy for you to overpay your taxes.
Here's how to Amend
My Return in TurboTax. It takes 12-14 weeks to process an amendment, so you cannot count on it being processed in time to pay your 2018 tax bill.
