Oklahoma Sole Proprietorship Tax Deadlines 2026

When is the Sole Proprietorship tax filing deadline in Oklahoma for 2026?

The Oklahoma Sole Proprietorship tax return is due Apr 15, 2026 for the 2026 tax year. An extension is available until Oct 15, 2026.

Does Oklahoma require Sole Proprietorship estimated tax payments?

Yes, Oklahoma requires estimated tax payments for Sole Proprietorship entities. The quarterly due dates are: Apr 15, 2026, Jun 15, 2026, Sep 15, 2026, Jan 15, 2027. Penalties may apply if you underpay or miss a deadline.

What form do I file for a Sole Proprietorship in Oklahoma?

Sole Proprietorship entities in Oklahoma file using Form State income tax return. You can download the form from Oklahoma Tax Commission at https://oklahoma.gov/tax.html.

Can I get an extension for my Oklahoma Sole Proprietorship tax return?

Yes. Oklahoma allows an extension for Sole Proprietorship returns until Oct 15, 2026. Note that an extension gives you more time to file, not more time to pay — any tax owed is still due by the original deadline of Apr 15, 2026.

What are the penalties for filing late in Oklahoma?

Oklahoma typically charges a failure-to-file penalty (usually 5% of unpaid tax per month, up to 25%) and a failure-to-pay penalty (usually 0.5-1% per month). Interest also accrues on unpaid balances. Filing for an extension by the original deadline avoids the failure-to-file penalty but not the failure-to-pay penalty.

Where can I file Oklahoma Sole Proprietorship taxes?

File through Oklahoma Tax Commission. Visit https://oklahoma.gov/tax.html for e-filing options, downloadable forms, and payment portals.