Filing Delaware business tax returns on time is essential to stay compliant and avoid penalties. However, if your business needs extra time to prepare accurate returns, Delaware allows tax extensions—provided you understand the rules, deadlines, and forms involved.
This comprehensive guide explains Delaware business income tax returns, required forms, extension eligibility, federal automatic extensions, state-specific extension forms, payment requirements, and mailing addresses.
Let’s dive deeper into how Delaware business tax extensions work for corporations, S-corporations, partnerships, trusts, and estates.
What Are Delaware Business Income Tax Returns?
Delaware imposes state business income taxes on corporations, S-corporations (for certain income components), partnerships, and fiduciaries (trusts and estates). Each business type files a specific return form, and understanding these forms is the first step toward proper filing or requesting an extension.
Below is an overview of each Delaware business income tax return:
Form CIT-TAX (formerly 1100) – Delaware Corporation Income Tax Return
Form CIT-TAX is filed by C-corporations operating in Delaware or earning income sourced to the state.
It reports:
- Delaware taxable income
- Adjustments from federal income
- Credits and deductions
- Estimated tax payments
- Balance due or refund
This form applies to traditional corporations with tax liability in the state. Delaware taxes corporate income at a fixed rate (currently 8.7%), making accurate reporting essential.
Form SCT-TAX – Delaware S-Corporation Income Tax Return
Although S-corporations themselves are typically not taxed at the federal level, Delaware requires SCT-TAX to:
- Report income, losses, and deductions
- Provide shareholder information
- Report certain corporate-level taxes (if applicable)
- Reconcile Delaware modifications
Shareholders also receive Schedule K-1 equivalents for personal reporting.
Form PRT-RTN – Delaware Partnership Return
Form PRT-RTN is the Delaware Partnership Return used by:
- General partnerships
- Limited partnerships (LP)
- Limited liability partnerships (LLP)
- Multi-member LLCs classified as partnerships for tax purposes
What Form PRT-RTN reports:
- Total partnership income
- Delaware-sourced income
- Modifications to federal income
- Partner names, FEINs, and allocation of income
- Nonresident withholding (if applicable)
Even though partnerships are pass-through entities, Form PRT-RTN must be filed annually to allocate Delaware source income to partners.
FORM FID-EST (FORMERLY 400-ES) – Delaware Fiduciary Income Tax Return (Trusts & Estates)
Form FID-EST is filed by:
- Estates
- Trusts
- Certain fiduciary entities
It reports:
- Delaware-sourced income
- Deductions
- Beneficiary distributions
- Taxable income
- Estimated tax payments
Trusts and estates with Delaware taxable income must file Form FID-EST, unless exempt.
When Is the Deadline to File Delaware Business Income Tax Returns?
Delaware follows due dates similar to federal filing deadlines, depending on entity type:
C-Corporations (Form CIT-TAX)
Form CIT-TAX is due by April 15 for calendar-year filers. For fiscal-year filers, Form CIT-TAX is due on the 15th day of the fourth month after the end of the taxable year.
S-Corporations (Form SCT-TAX)
Form SCT-TAX is due by March 15 for calendar-year filers. For fiscal-year filers, Form SCT-TAX is due on the 15th day of the third month after the end of the taxable year.
Partnerships (Form PRT-RTN)
Form PRT-RTN is due by March 15 for calendar-year filers. For fiscal-year filers, Form 300 is due on the 15th day of the third month after the end of the taxable year.
Trusts & Estates (Form FID-EST)
Form FID-EST is due April 15 for calendar-year filers. For fiscal-year filers, Form FID-EST is due on the 15th day of the fourth month after the close of the taxable year.
Missing these deadlines may result in penalties and interest—unless the business files a valid extension.
Does Delaware Support Tax Extensions for Business Income Tax Returns?
Yes. Delaware does support business tax extensions, but the state has a unique rule:
Delaware accepts a federal extension (Form 7004) as a valid state extension.
This means if your business files Federal Form 7004 and it is approved, Delaware automatically grants the same extension period for your state return.
No separate Delaware extension form is required if you already have an approved federal extension.
However, there are exceptions — and that’s where state extension forms come in.
When Do Businesses Need to File a Delaware State-Specific Extension Form?
Businesses must file a Delaware extension form only if they do NOT have an approved federal Form 7004 extension.
If you do not file or are not approved for a federal extension, you must file seperate state specific extension Form.
Form CIT-EXT – Extension for Form CIT-TAX (Corporations)
The CIT-EXT is a Request for Extension form that allows corporations operating in Delaware to receive extra time to file their annual corporate income tax return. When submitted properly and on time, the form generally grants a six-month extension to file. However, this extension applies only to the filing of the tax return—not the payment. Corporations estimating that they owe tax must calculate and pay those amounts along with the extension request to avoid penalties and interest.The form includes a worksheet to help businesses estimate their tax liability.Corporations that already have a valid federal extension typically receive an automatic extension in Delaware, but the CIT-EXT is used when a state-specific request is needed.
The CIT-EXT must be submitted on or before the original due date of the corporate income tax return.
Form SCT-EXT – Extension for Form SCT-TAX (S-Corporations)
SCT-EXT is the Delaware form that S-Corporations use to request additional time to file their annual Delaware S-Corporation tax return. This extension gives more time to file, but does not extend the deadline to pay any tax or nonresident shareholder withholding owed.
S-Corporations should use this form when they cannot complete their Delaware return by the normal due date. If the business has nonresident shareholders, SCT-EXT also requires a calculation of estimated withholding based on distributive income and the percentage of stock owned by nonresidents.The form includes a worksheet to help businesses estimate their tax liability.
S-Corporations that already have a valid federal extension typically receive an automatic extension in Delaware, but the SCT-EXT is used when a state-specific request is needed.
Form PRT-EXT – Extension for PRT-RTN (Partnerships)
PRT-EXT is the form used by partnerships doing business in Delaware to request an extension of time to file their state partnership return (PRT-RTN).Partnerships should use this form when they cannot complete their Delaware return by the normal due date.If a federal extension has been secured, that may automatically extend the Delaware return deadline as well. Otherwise, you use PRT-EXT to request an independent state-level extension.Filing an extension does not necessarily extend the time to pay any tax liability — it’s just an extension to file the return.
Form FID-EXT – Extension for FID-TAX (Fiduciary Income Tax Return)
Trust and Estates who need more time to file their Delaware Fiduciary Income Tax Return (Form FID-TAX) can request an automatic filing extension by submitting Form FID-EXT on or before the original due date, April 30. This automatic extension moves the filing deadline to October 15. When submitting the extension request, fiduciaries must pay any estimated tax due for the year. Unpaid balances accrue interest at ½% per month from the original due date until paid.If additional time is required beyond October 15, a fiduciary may file a photocopy of an approved Federal Fiduciary Extension before the automatic extension expires. A copy of this approved federal extension must also be attached when filing the Delaware return. Once accepted, the federal extension aligns the Delaware filing deadline with the extended federal due date.
Key Rule:
Delaware only requires these state extension forms if you do NOT obtain an approved federal extension.
How Do I Pay Balance Tax Due When Filing a Delaware Extension?
A tax extension only extends the time to file, not the time to pay.
To avoid penalties and interest:
- Estimate your Delaware tax liability
- Pay the amount due when filing your extension request
Payments can be made:
1. Electronically through the Delaware Tax Portal
The Delaware Division of Revenue allows electronic payments, including:
- Credit/debit card
- ACH debit
- ACH credit
- Online tax portal payment
2. By Check or Money Order (mailed with extension form)
Include:
- Business name
- EIN
- Tax year
- Tax type
- Applicable extension form
Failure to pay at extension time leads to late payment penalties even if the extension is approved.
Where Do I Mail Delaware Extension Forms (CIT-EXT, SCT-EXT, PRT-EXT, and FID-EXT)?
If you are mailing your Delaware business tax extension form with remittance (payment), use the correct address for each form:
1. Mailing Address for Form CIT-EXT (Corporations)
If you are submitting Form CIT-EXT with payment:
- Delaware Division of Revenue
P.O. Box 830
Wilmington, DE 19899-0830
2. Mailing Address for Form SCT-EXT (S-Corporations)
If you are submitting Form SCT-EXT with payment:
- Delaware Division of Revenue. PO Box 0830 Wilmington, DE 19899-0830
3. Mailing Address for Form FID-EXT (Trusts & Estates)
If you are submitting Form FID-EXT with payment:
- Delaware Division of Revenue. PO Box 0830 Wilmington, DE 19899-0830
3. Mailing Address for Form PRT-EXT (Trusts & Estates)
- Delaware Division of Revenue. PO Box 0830 Wilmington, DE 19899-0830
What are the Penalties for Not Filing Delaware Business Returns or Not Requesting an Extension
Failing to file your Delaware business tax return on time—or failing to apply for a valid extension—can result in significant penalties, interest, and additional compliance consequences. The Delaware Division of Revenue enforces penalties differently depending on the type of business entity and the form required.
Below is a complete breakdown of penalties associated with Form PRT-RTN (Partnerships), Form CIT-TAX (Corporations), Form SCT-TAX (S-Corporations), and Form FID-EST (Trusts & Estates).
1. Penalties for Partnerships — Form PRT-RTN
Failure to File Penalty
Partnerships that fail to file Form PRT-RTN or fail to provide the required information are subject to:
- $25 per partner per month,
- Up to a maximum of 5 months.
This means partnerships with more partners will incur higher penalties, as the penalty is multiplied by the number of partners during any part of the tax year.
Negligence or Fraud Penalties
Delaware imposes severe penalties for:
- Filing a false or fraudulent return
- Making false certifications
- Intentional underreporting of income or withholding
Using federal return figures does not shield a partnership from penalties if the information is incorrect or incomplete on the Delaware return.
2. Penalties for Corporations — Form CIT-TAX
Late Filing Penalty
For C-corporations filing Form CIT-TAX:
- 5% of the tax due per month,
- Up to a maximum of 50% of the unpaid tax.
Interest Charges
- ½% (0.5%) interest per month is added to the unpaid tax,
- Calculated from the original due date until payment is made.
Late Payment Penalty
In addition to the above:
- 1% per month penalty for failure to pay,
- Capped at 25% of the unpaid tax shown on a timely filed return.
This means even if the return is filed on time, failing to pay the tax due triggers a separate penalty.
3. Penalties for S-Corporations — Form SCT-TAX
S-corporations filing Form SCT-TAX face penalties similar to C-corporations if the return is late or tax is unpaid.
Late Filing Penalty
- 5% of the tax liability per month,
- Up to a maximum of 50%.
Interest on Unpaid Tax
- ½% (0.5%) interest per month on the outstanding tax from the original due date.
Late Payment Penalty
- 1% per month,
- Capped at 25% of the unpaid amount shown on a timely filed return.
Even though S-corps generally don’t pay entity-level income tax, they may still owe nonresident withholding or other Delaware taxes that trigger these penalties.
4. Penalties for Trusts & Estates — Form FID-EST
Trusts and estates filing Form FID-EST may owe estimated tax during the year. Penalties apply when required estimates are not paid correctly.
Penalty for Underpayment of Estimated Tax
Delaware imposes:
- 1½% (1.5%) per month,
- Or fraction of a month,
- On the amount of underpaid estimated tax.
How to Avoid the Estimated Tax Penalty
The penalty does not apply if each installment is paid on time and meets either of the following safe harbor rules:
- Payment equals 90% of the current year’s tax, OR
- Payment is based on 100% of last year’s taxable income using the current year’s tax rate.
These rules are designed to help taxpayers avoid penalties when income fluctuates during the year.
Final Thoughts
Delaware’s business tax extension system is simple once you understand the rules:
If you have an approved Federal Form 7004, you automatically receive a Delaware extension—no need for a separate state form.
But if you do not obtain a federal extension, Delaware requires you to file a state-specific extension form such as Form CIT-EXT, SCT-EXT, PRT-EXT, or FID-EXT.
Remember that an extension gives you more time to file, not more time to pay. Estimating and paying your tax balance with your extension request prevents penalties and ensures compliance.
With proper planning and timely submissions, your business can stay fully compliant with Delaware tax law while gaining the additional time needed to prepare accurate returns.
