504-C: 2025 Form 504-C Application for Extension of Time to File an Oklahoma Income Tax Return for Corporations, Partnerships and Fiduciaries (2025)
Oklahoma · Oklahoma Tax Commission · Used for tax years 2025
Form 504-C requests additional time to file an Oklahoma income tax return for corporations, partnerships and fiduciaries. It reports estimated income tax liability, withholding, payments, credits and any balance due. It extends the time to file, not the time to pay tax.
Who files this form
Corporations, partnerships and fiduciaries use Form 504-C to request more time to file their 2025 Oklahoma income tax return when they:
- Owe additional Oklahoma income tax.
- Do not have a federal extension.
- Need more time beyond the federal extension.
If you have an automatic federal extension and no additional Oklahoma tax is due, Oklahoma honors that extension. Provide a copy of the federal extension when you file your Oklahoma return.
Electing pass-through entities use Form 504-PTE instead. Individuals use Form 504-I.
What you'll need
Have the following information ready to complete Form 504-C:
- The entity's name, mailing address and Federal Employer Identification Number.
- The tax year and return type: Form 512, 512-E, 512-S, 513, 513-NR or 514.
- Your federal extension date, if applicable, and the Oklahoma extension date you are requesting.
- A reason if you need time beyond the federal extension.
- Your estimated total income tax liability, Oklahoma tax withheld, estimated payments, prior-year overpayment credited, and other expected payments and credits.
- The amount of income tax you are paying.
If relying on the federal extension, provide a copy with your Oklahoma return. If you pay the extension payment electronically, keep the confirmation number and provide a copy of Form 504-C when you file your income tax return.
How to file
Complete the entity information, check the return type, enter the extension dates and complete the income tax computation. The form includes a signature line for an officer, partner, member or fiduciary and a separate paid preparer's signature line.
By mail: Send Form 504-C with payment, if applicable, to:
Oklahoma Tax Commission
PO Box 26890
Oklahoma City, OK 73126-0890
The application must be postmarked on or before the income tax return's filing due date, or before the automatic federal extension expires.
Electronic payment: Make an extension payment at oktap.tax.ok.gov. Some electronic payment services charge a convenience fee. Keep your confirmation number.
If you make the extension payment electronically, do not mail Form 504-C. Provide a copy of Form 504-C when you file your income tax return.
Common mistakes
- Treating the extension as extra time to pay. Form 504-C extends filing time only, not payment time.
- Not paying enough by the original due date. The extension is valid only if at least 90% of the tax liability is paid by that date.
- Leaving line 1 blank. You must enter your total income tax liability. You may estimate it. Enter “0” if you do not expect to owe tax.
- Mailing Form 504-C after paying electronically. Do not mail it in that case. Instead, provide a copy when you file your income tax return.
- Using the wrong extension form. Electing pass-through entities use Form 504-PTE, and individuals use Form 504-I.
Questions people ask
Do I need Form 504-C if I already have a federal extension?
Not if no additional Oklahoma tax is due and you only need the time covered by the automatic federal extension. Provide a copy of the federal extension with your Oklahoma return. Use Form 504-C if you owe additional Oklahoma tax or need time beyond the federal extension.
How long can an extension be?
For partnerships and fiduciaries, the extension cannot exceed half the accounting period covered by the return. For example, a 12-month tax year allows a 6-month extension. For corporations, the total extension cannot exceed 7 months.
Does paying 90% prevent all penalties and interest?
No. Paying at least 90% by the original due date is required for a valid extension. A 5% delinquent penalty may apply if less than 90% is paid by that date. Unpaid tax is subject to interest at 1.25% per month from the original due date until paid.
Can I estimate my tax liability?
Yes. Line 1 allows an estimate of your total income tax liability. You must enter an amount, including “0” if you do not expect to owe tax.