OW-8-P: 2025 Form OW-8-P Underpayment of Estimated Tax Worksheet (2025)
Oklahoma · Oklahoma Tax Commission · Used for tax years 2025
Oklahoma Form OW-8-P is a worksheet for figuring underpayment of estimated tax and any interest due for 2025. It calculates required payments, compares them with withholding and estimated tax payments, and figures interest for each quarter.
Who files this form
Use Form OW-8-P to work out whether you owe interest for underpaying Oklahoma estimated tax for tax year 2025.
If you use the annualized income installment method, you must check the box in Section One and provide this worksheet with your return, along with:
- Form OW-8-P-SUP-I for individuals.
- Form OW-8-P-SUP-C for corporations, S corporations, exempt organizations, partnerships and trusts.
The worksheet includes several stopping points where you do not owe interest, including when line 3 is less than $1,000 or line 6 is less than $500.
When it's due
For tax year 2025, the worksheet prints these estimated tax installment due dates:
- First quarter: April 15.
- Second quarter: June 15.
- Third quarter: September 15.
- Fourth quarter: January 15 of the following year.
The Part 3 instructions say to adjust a preprinted date to the next business day if it falls on a weekend or holiday.
What you'll need
Have these items available to complete the worksheet:
- Your name as shown on your return and your SSN or FEIN.
- Your 2025 income tax return figures, including income tax, Oklahoma refundable and nonrefundable credits, and withholding.
- Your previous year's tax liability. That return must cover 12 months.
- Estimated tax payment amounts and the dates paid, plus any other tax payments used in Part 3.
- Any overpayment from your previous year's return that you elected to apply to this year's estimated tax.
If you use the annualized method, complete and provide the applicable Form OW-8-P-SUP-I or OW-8-P-SUP-C with this worksheet and your return. These forms are available at tax.ok.gov.
If you need more lines for tax payments in Part 3, attach a schedule listing each payment separately using Columns A through E.
How to file
If you check the annualized-method box, provide Form OW-8-P and the applicable supplemental form with your tax return.
Enter the total interest from line 19 on your income tax return as well as on this worksheet.
The supplied form does not give a mailing address or e-file instructions.
Common mistakes
- Do not include estimated tax payments on line 5. That line is for withholding only.
- On line 10, enter estimated tax in the quarter when it was paid. Include any previous-year overpayment applied to this year's estimated tax in the first quarter.
- Do not include payments made after the fourth-quarter estimate's due date as estimated tax on line 10. Use them as prepayments in Part 3 instead.
- Treat withholding as paid one-fourth on each installment due date unless you can show otherwise.
- Complete lines 11 through 17 for one column before moving to the next column. Complete Part 3 before lines 18 and 19.
- In Part 3, apply the earliest payment first and use only the portion needed to bring the balance to zero. Do not reuse amounts already applied to earlier quarters.
- Complete each quarter in Part 3 before starting the next. Bring Column C to zero unless all payments have already been applied.
Questions people ask
Can the annualized method help if my income varied during the year?
Yes. The form says this method may lower or eliminate one or more required installments if your income varied, such as from a seasonal business. Check the Section One box and complete the required supplemental form.
How is the required annual payment calculated?
Line 8 uses the smaller of 70% of your Oklahoma tax liability on line 3 or the tax liability shown on your previous year's return. The previous year's return must cover 12 months.
What if I was not required to file a return for the previous tax year?
The worksheet says to stop at line 7. You do not owe the interest.
What if my payments covered every required installment?
If line 10c, withholding plus estimated tax paid, equals or exceeds line 9 for every payment period, stop. You do not owe the interest.
How does Part 3 calculate interest?
For each line, multiply the balance in Column C by the number of days in Column D and by 20%, then divide by 365. Transfer each quarter's interest to line 18, add the quarters on line 19, and enter the total on your income tax return.