Delaware Form 1100 Corporation Income Tax Return: Filing, Deadlines, and Credits

Delaware Form 1100, now officially titled Form CIT-TAX, is the state’s annual corporate income tax return. Every corporation doing business in Delaware or earning income from Delaware sources files it, starts the calculation from federal taxable income, applies Delaware-specific adjustments, apportions multistate income using a single sales factor, and pays tax at a flat 8.7 percent rate.¹ Calendar-year filers owe the return by April 15, and the Division of Revenue accepts both electronic and paper submissions.

Who Has to File

Any domestic or foreign corporation doing business in Delaware, or earning income from Delaware sources, must file Form CIT-TAX. This holds whether the year ended in a profit or a loss, and even when total tax liability comes to zero.²

Delaware does not accept consolidated returns. Each member of a federal consolidated group files its own separate Delaware return, using a pro forma Form 1120 that reports income and deductions as if the member had filed a separate federal return.³

Corporations That Are Exempt

Section 1902(b) of Title 30 removes several categories from the corporate income tax:

S corporations with a valid federal S election. They file Form SCT-RTN (formerly Form 1100S) to report shareholder information but owe no entity-level tax.⁴
Holding and investment management companies whose Delaware activity is limited to maintaining and managing intangible investments such as stocks, bonds, and patents. These still file an Annual Information Return on Form CIT-HIC.²
Corporations that keep a registered Delaware office but do not conduct business in the state.⁴
Insurance companies that pay premium taxes to the Insurance Commissioner.
Religious, charitable, scientific, and educational nonprofits, along with fraternal societies, business leagues, civic leagues, and social clubs, provided no earnings benefit private individuals.

A holding company loses the exemption if it drifts beyond managing intangible investments, so periodic review of actual activity matters.

Calculating Delaware Taxable Income

The computation begins with federal taxable income from your pro forma Form 1120 and moves through two adjustments: Delaware modifications under Section 1903, and apportionment for multistate filers.⁵

Add-Backs

State and local income taxes deducted on the federal return, including Delaware’s own tax.
Interest on bonds issued by other states or their political subdivisions, which is normally exempt federally.

Subtractions

Interest on Treasury bonds and other U.S. government obligations, minus any expenses allocable to earning it.
Dividends, interest, and royalties from foreign corporations on which a foreign tax was paid or deemed paid.
Gains and losses on U.S. or Delaware government securities, with related expenses backed out as well.
Excess percentage depletion on oil and gas, meaning the portion over cost depletion.
Wages disallowed federally because a jobs tax credit was claimed.

The result is Delaware “entire net income.” If every dollar comes from Delaware sources, that figure flows straight into the tax calculation. Otherwise, apportion.

Single Sales Factor Apportionment

Starting with the 2020 tax year, Delaware apportions multistate income using a single factor: Delaware gross receipts divided by total U.S. gross receipts.³ Multiply that ratio by entire net income to get Delaware taxable income.⁶ Property and payroll in Delaware no longer pull income into the state, which generally favors corporations with heavy in-state operations but out-of-state customers, and increases the Delaware share for sellers with lots of Delaware customers but little physical footprint.

Walking Through the Form

The current CIT-TAX and its instructions are on the Delaware Division of Revenue’s business tax forms page. The numbered lines follow the computation above:

Line 1 — Federal taxable income from pro forma Form 1120. Consolidated-group members use separate-company numbers, not the group’s consolidated figure.
Lines 2 and 3 — Add back state and local income taxes and interest on other states’ obligations.
Line 4 — Subtract U.S. government interest, foreign-taxed income, and the other items on the form’s schedule.
Line 5 — Entire net income: federal taxable income plus additions, minus subtractions.
Lines 6 through 11 — If any income comes from outside Delaware, complete the sales factor schedule, enter Delaware and total U.S. gross receipts, compute the ratio, and apply it to Line 5.
Line 12 — Delaware taxable income: the lesser of Line 5 or Line 11.
Line 13 — Tax liability: Line 12 times 8.7 percent.¹
Remaining lines — Subtract credits, estimated tax already paid, and extension payments. The balance is what you owe or what Delaware owes back.

What to Attach

Every filer attaches a complete copy of the pro forma federal return with all schedules.² If you took a federal extension, include that too. Corporations with assets of $10 million or more that file Schedule M-3 federally should attach that schedule as well, since it carries the book-to-tax reconciliation Delaware may reference.⁷

Filing Deadline and Extensions

Form CIT-TAX is due on the 15th day of the fourth month after the close of your tax year — April 15 for calendar-year filers.² A June 30 fiscal-year corporation, for example, would file by October 15.

A federal extension automatically extends the Delaware filing deadline by six months, with no separate Delaware extension form required just for the time.² Attach a copy of the federal extension when you eventually file. The extension covers only the paperwork; tax owed is still due on the original date. If you expect a balance, file Form CIT-EXT with a payment by the original deadline to limit penalties and interest.³

Estimated Tax Payments

Delaware splits estimated tax into four unequal installments, which is not the standard 25-25-25-25 most states use:⁶

50 percent by the first day of the fourth month of the tax year (April 1 for calendar-year filers)
20 percent by the 15th day of the sixth month (June 15)
20 percent by the 15th day of the ninth month (September 15)
10 percent by the 15th day of the twelfth month (December 15)

Underpaying or missing any installment triggers a penalty of 1.5 percent per month on the shortfall. You avoid the penalty if timely payments total at least 80 percent of this year’s liability or 100 percent of last year’s. Small corporations, defined as those with aggregate gross receipts of $20 million or less in at least two of the three preceding years, can use that threshold when checking whether their estimates were enough.³

How to Submit

You can file electronically through the Delaware Taxpayer Portal or mail a completed fillable PDF of Form CIT-TAX from the Division’s business tax forms page.⁸ The current instructions list separate mailing addresses depending on whether a payment is enclosed, and the addresses can change year to year, so check the current booklet.

Keep copies of the return, all schedules, the pro forma federal return, and proof of payment. Delaware requires corporations to maintain records for at least three years after filing.⁴

Penalties for Filing or Paying Late

Late-filed return: 5 percent per month (or partial month) on unpaid tax, capped at 50 percent of the liability, plus interest of 0.5 percent per month running from the original due date.³
Tax shown on a timely return but unpaid: an additional 1 percent per month, capped at 25 percent of the unpaid amount.³
Estimated tax shortfall: 1.5 percent per month on each underpaid or late installment from its due date until paid.⁶

Willful failure to file, pay, or allow examination of corporate records can bring a fine up to $3,000, imprisonment up to six months, or both. The same criminal penalty applies to a false or fraudulent return.⁹

Credits That Reduce the Tax

Delaware offers several credits taken on Form CIT-TAX with supporting schedules attached. Most cannot drive liability below zero, and carryforward rules vary by credit.

New Economy Jobs Credit for employers adding at least 50 new jobs in prescribed salary ranges, worth up to 40 percent of withholding taxes collected on behalf of new employees, with bonuses for targeted growth zones and former brownfield sites.
Research and Development Credit for new research activity in Delaware, authorized under Title 30, Chapter 20, Section 8.
Historic Preservation Credit covering 20 to 40 percent of qualified restoration spending on historic properties. The credit is nonrefundable but can be sold or transferred.
New Business Facility Credit for startups and new facilities that create at least five jobs and invest at least $200,000, with enhanced amounts for brownfield locations and clean energy device manufacturers.
Land and Historic Resource Conservation Credit equal to 40 percent of the fair market value of eligible land donated to a public agency or qualifying nonprofit, capped at $40,000 per calendar year.

Each credit has its own eligibility rules and application steps, so confirm current requirements before claiming any of them on the return.

1
Justia. Delaware Code 30-1902 – Imposition of Tax on Corporations; Exemptions
2
Delaware Division of Revenue. Corporate Income Tax FAQs
3
Delaware Division of Revenue. Corporate Income Tax Instructions
4
Delaware Code Online. Delaware Code 30 – Corporation Income Tax
5
Justia. Delaware Code 30-1903 – Computation of Taxable Income
6
Delaware Division of Revenue. Filing Corporate Income Tax
7
Internal Revenue Service. About Form 1120, U.S. Corporation Income Tax Return
8
Delaware Division of Revenue. Business Tax Forms
9
Justia. Delaware Code 30-1912 – Penalties – Late Filing; Failure to File Returns; False and Fraudulent Return; Failure to Maintain Records