C Corporation Tax Deadlines in Oklahoma
Federal and state filing dates, extensions, and estimate schedules for 2026.
Oklahoma filing deadline
Calendar-year due date follows federal timing for corporations.
Due: Apr 15, 2026
Extension: Oct 15, 2026
Form: State corporate income tax return
Estimated payments
Estimated payment dates: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026.
Due: Apr 15, 2026
FAQ
Does Oklahoma require C Corporation estimated payments?
Estimated payments are scheduled for Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Dec 15, 2026.
Where can I file Oklahoma C Corporation taxes?
Use Oklahoma Tax Commission resources at https://oklahoma.gov/tax.html for forms and filing instructions.