Oklahoma tax deadlines in 2026: filing dates and estimated payments
Deadlines that fall in calendar 2026: the 2025 return and the 2026 estimated payments. Different year? See Oklahoma 2025 →
Oklahoma deadlines in 2026
| 2025 individual return due | April 15, 2026 |
|---|---|
| Extended filing deadline | October 15, 2026 |
| Payment due | April 15, 2026, extension or not |
| Final 2025 estimated payment | January 15, 2026 |
| 2026 estimated payments | April 15, 2026 · June 15, 2026 · September 15, 2026 · January 15, 2027 |
Conforms to April 15. Taxpayers who file and pay electronically are granted until April 20.
Oklahoma estimated tax payments in 2026
You must make equal quarterly estimated payments if you can reasonably expect your tax liability to exceed your withholding by $500 or more and you expect your withholding to be less than the smaller of 70% of your current year's tax liability or the tax shown on your prior-year return.
| Q1 (2026 tax year) | April 15, 2026 |
|---|---|
| Q2 (2026 tax year) | June 15, 2026 |
| Q3 (2026 tax year) | September 15, 2026 |
| Q4 (2026 tax year) | January 15, 2027 |
| Voucher | Form OW-8-ES, Oklahoma Individual Estimated Tax Declaration |
| Underpayment safe harbor | Underpayment interest (20% per year) applies if tax liability exceeds withholding by $500 or more and timely estimated payments plus withholding are not at least 70% of the current-year tax liability or 100% of the prior-year tax liability; no interest if the tax shown on the return is less than $1,000. |
| Pay online | oktap.tax.ok.gov |
Estates and farmers (at least two-thirds of gross income from farming) are not required to make estimated payments. Uneven income may use the annualized installment method on Form OW-8-ES-SUP.
Source: oklahoma.gov, read September 3, 2026. “Due Dates (Calendar year): 1st Quarter - April 15, 2nd Quarter - June 15, 3rd Quarter - September 15, 4th Quarter - January 15”
All 51 jurisdictions in one table: state estimated tax payment dates for 2026.
Oklahoma extensions
Every state's rule in one table: which states accept the federal extension in 2026.
| Does Oklahoma accept the federal extension? | Only in some cases. See the rule below. |
|---|---|
| State extension form | Form 504-I |
| Original due date | April 15, 2026 |
| Extended due date | October 15, 2026 |
| Payment | Still due April 15, 2026. The extension is to file, not to pay. The extension is valid only if 90% of the tax liability is paid by the original due date; a 5% penalty may apply if less than 90% is paid. |
| How to get it | With a federal extension and no additional Oklahoma tax due, just provide a copy of the federal extension with the Oklahoma return; file Form 504-I with payment if you owe Oklahoma tax or have no federal extension. |
Source: oklahoma.gov, read September 3, 2026. “the Oklahoma Tax Commission has administratively adopted the policy of honoring the automatic federal extension, when no additional state tax is due, as an extension of time to file the Oklahoma return.”
Federal deadlines in 2026
| 2025 Form 1040 | April 15, 2026 · extension October 15, 2026 |
|---|---|
| 2025 S-corp (1120-S) & partnership (1065) | March 16, 2026 |
| 2025 C-corp (Form 1120) | April 15, 2026 |
| 2026 federal estimated payments (1040-ES) | April 15, 2026 · June 15, 2026 · September 15, 2026 · January 15, 2027 |
Source: IRS Publication 509 and Form 1040-ES instructions, irs.gov.
Frequently asked questions
When are Oklahoma state taxes due in 2026?
Your 2025 Oklahoma individual income tax return is due April 15, 2026. If that date falls on a weekend or legal holiday, the deadline moves to the next business day. An extension moves the filing deadline to October 15, 2026, but any tax owed is still due on the original date.
When are Oklahoma estimated tax payments due in 2026?
Oklahoma estimated payments for the 2026 tax year are due April 15, 2026, June 15, 2026, September 15, 2026, January 15, 2027. Use Form OW-8-ES, Oklahoma Individual Estimated Tax Declaration or pay online. The final installment for 2025 was due January 15, 2026.
Does Oklahoma accept the federal extension?
Only in some cases. See the rule below. The state form is Form 504-I. The extended filing deadline is October 15, 2026, and tax is still due by April 15, 2026.
Does a Oklahoma extension give me more time to pay?
No. An extension extends the time to file, not to pay. To avoid penalties and interest, pay what you expect to owe by April 15, 2026.
Dates are the statutory deadlines that fall in 2026 and move to the next business day when they land on a weekend or holiday. Each section links to the source it was checked against. Always confirm with the Oklahoma tax agency or the IRS before relying on a date. This is general information, not tax advice.