83-305: Underestimate of Corporate Income Tax Worksheet (2025)
Mississippi · Mississippi DOR · Used for tax years 2025
Mississippi Form 83-305 is a worksheet for calculating required quarterly estimated income tax payments and interest and penalties for underestimated tax. It uses current and prior year income tax, quarterly payments, and overpayments to calculate the total interest and penalty d
Who files this form
The 2025 worksheet includes entries for corporations, composite S corporations, and electing pass-through entities. It also provides a reporting line for insurance filers.
The form calculates underestimated income tax interest and penalties, but it does not state which taxpayers are required to complete it.
When it's due
For tax year 2025, the worksheet lists these estimated payment due dates:
- Column (a): 15th of the 4th month.
- Column (b): 15th of the 6th month.
- Column (c): 15th of the 9th month.
- Column (d): 15th of the 12th month.
Enter the applicable dates on line 6.
What you'll need
Have these figures and details available to complete the worksheet:
- Your FEIN.
- Current-year income tax due from Form 83-105, line 8, for corporations, or Form 84-105, line 8, for composite S corporations and electing pass-through entities.
- Prior-year income tax due.
- Estimated tax paid each quarter and payment dates.
- Any overpayment from the prior year or earlier quarters.
The form does not provide a separate list of required supporting documents.
Common mistakes
- Overlooking the large-corporation exception. Line 4 generally tells you to use the lesser of lines 2 and 3, but it specifically says that large corporations should see the instructions. Those instructions are not included in the supplied text.
- Entering a negative amount where zero is required. Lines 11 and 14 specifically direct you to enter zero if the result is negative.
Questions people ask
Where do I find the current-year income tax amount?
Use Form 83-105, line 8, for corporations, or Form 84-105, line 8, for composite S corporations and electing pass-through entities. Enter it on worksheet line 1.
How is the quarterly estimated payment calculated?
Line 2 is 90% of current-year income tax due. Line 4 generally uses the lesser of that amount or prior-year income tax due, with an exception for large corporations. Divide line 4 by four to get the quarterly payment on line 5.
What interest rate does the worksheet use?
Line 15 says to compute interest at 5/10 of 1% per month, from the payment due date until the payment is made or the next payment due date, whichever is earlier.
Where does the total interest and penalty go?
Add total penalty on line 17 and total interest on line 18 to get line 19. Enter that total on Form 83-105, page 1, line 15, for corporations; Form 84-105, page 1, line 15, for composite S corporations and electing pass-through entities; or Form 83-391, line 10, for insurance.