Always confirm the current year’s dates with the IRS and the California Franchise Tax Board directly. Dates move for weekends and holidays, and California has repeatedly postponed deadlines for counties under a disaster declaration. We do not publish a date list here precisely because a stale one is worse than none.
The structure that does not change
The individual filing deadline
Individual returns are due in mid-April for the previous calendar year, for both federal and California purposes.
Extensions
An extension moves your filing deadline to October. California grants an automatic extension to individuals without a form, where the IRS requires one to be filed. Either way, the critical point is below.
Estimated payments
Self-employed people and anyone with substantial untaxed income generally pay quarterly. California’s instalment percentages are not evenly spread across the four payments the way the federal ones are — a common and expensive assumption.
An extension to file is not an extension to pay. If you owe, the money is still due in April. Filing an extension and paying nothing means interest and penalties accrue from the original date. If you cannot pay in full, file anyway and arrange a payment plan — the failure-to-file penalty is substantially harsher than the failure-to-pay one.
If you are behind
Filing late is recoverable and extremely common. Both the IRS and the FTB run instalment agreements, and the IRS operates a first-time penalty abatement for otherwise compliant taxpayers. This is a good reason to hire someone credentialed with representation rights — see which credential does what.