For California:
If you cannot file your personal income tax return by the April 18 deadline, but will have a refund or no balance due, you automatically get a 6-month extension to file your tax return by October 16 for that tax year. If your return will show a balance due, you need to make an extension payment by the April 18 deadline, that will cover your tax liability, to receive the filing extension and avoid late payment penalties and interest.