Delaware Quarterly Taxes: Due Dates, Safe Harbor, and Penalties

Delaware quarterly taxes are estimated income tax payments made throughout the year by people and businesses whose withholding won’t cover their bill. For individuals, you owe them if you expect your Delaware tax to exceed withholding by more than $800.¹ For corporations, the requirement is broader: every domestic or foreign corporation that isn’t specifically exempt must file an annual tentative return and make estimated payments regardless of the amount expected to be owed.² Miss a payment or short one, and Delaware layers penalties that can reach 1.5% per month on top of interest and a separate failure-to-pay penalty.

Individual Due Dates

For calendar-year taxpayers, the four installments fall on:

April 30 (first installment)
June 15 (second installment)
September 15 (third installment)
January 15 of the following year (fourth installment)

You can also pay the full estimated amount with the April declaration rather than splitting it into four.¹

Fiscal-year filers use the 30th day of the fourth month and the 15th day of the sixth and ninth months of the fiscal year, plus the 15th day of the first month of the following fiscal year.¹

Note the first-quarter deadline: April 30, not April 15. The federal first-quarter estimated payment is due April 15, so your state and federal deadlines are two weeks apart.³

Corporate Due Dates

Corporate installments are not equal for most companies. A standard calendar-year corporation pays:

April 15 — 50% of estimated tax, filed with Form 1100-T
June 15 — 20%
September 15 — 20%
December 15 — 10%

Small corporations, defined as those with aggregate gross receipts and gross income not exceeding $20 million for any two of the three preceding tax years, pay four equal installments of 25% on the same dates.² Fiscal-year corporations follow the same percentage splits anchored to the 15th day of their fourth, sixth, ninth, and twelfth months.

The front-loading trips up businesses used to the federal system. A standard corporation budgeting for four equal quarterly payments will come up short on April 15, when half the annual estimate is due. The corporate income tax rate itself is 8.7% of federal taxable income allocated and apportioned to Delaware.⁴

How Much to Pay

Start with your projected Delaware taxable income for the year and apply the graduated rate structure, which runs from 0% on the first $2,000 up to 6.6% on income above $60,000.⁵ Subtract expected withholding. What’s left is what you split into installments on Form 200-ES.

Safe Harbor

You avoid the estimated tax penalty if each installment is paid on time and meets one of two tests: the payment equals at least 90% of the current year’s tax, or the payment is based on last year’s taxable income calculated at the current year’s rates.⁶ The prior-year option is useful when income is rising: last year’s number can keep you penalty-free even if you end up owing more this year.

Delaware’s safe harbor doesn’t include the higher-income surcharge that federal rules impose. The IRS requires 90% of current-year tax or 100% of prior-year tax, and that 100% climbs to 110% if prior-year AGI exceeded $150,000 (or $75,000 if married filing separately).⁷ So a high earner’s state and federal payments may need to be different amounts.

Uneven Income

If your income arrives unevenly, such as a large fourth-quarter capital gain or a seasonal business earning most of its revenue in summer, use Delaware’s annualized income installment method. It calculates each installment based on income actually earned during that period rather than assuming one-fourth of annual income arrived each quarter. You report it on Form PIT-UND, and it can reduce or eliminate underpayment penalties for irregular income patterns.⁸

Adjusting Mid-Year

When income, deductions, or exemptions change substantially after you’ve started paying, recalculate and adjust the remaining installments. The adjustment deadlines track the installment deadlines: a change between April 1 and June 1 gets picked up starting June 15; a change between June 1 and September 1 by September 15; and a change between September 1 and year-end by January 15.¹

How to File and Pay

Individuals file Form 200-ES, which includes a tax computation worksheet that walks through gross income, deductions, and the graduated rate table to arrive at each quarterly amount. Corporations file Form 1100-T, the Tentative Tax Return, rather than a separate estimated tax voucher.

Electronic payments for both individuals and businesses go through the Delaware Taxpayer Portal at tax.delaware.gov.⁹ You can also mail a check or money order payable to the Delaware Division of Revenue with the appropriate form. If you mail close to the deadline, the postmark date counts as the filing date.

What Happens If You’re Late or Short

Delaware charges three separate amounts, and they run concurrently:

Interest of 0.5% per month, or fraction of a month, on any unpaid tax from the original due date until payment.¹⁰
A failure-to-pay penalty of 1% per month, capped at 25%, on the net tax liability shown on the return.¹¹
A penalty of 1.5% per month for failure to file or pay estimated taxes, computed on the tax payment and assessed in addition to the other two.¹¹

Miss a quarterly payment and then pay late on the annual return, and all three can hit at once. For corporations that file the annual return late, the penalty is 5% per month plus 0.5% monthly interest from the original due date, with an additional 1% per month, capped at 25%, for failure to pay the liability on a timely filed return.¹² Meeting the 90%-of-current-year or prior-year-at-current-rates safe harbor avoids the estimated tax penalty entirely.⁶

Extensions Don’t Extend Payment

For corporations, a federal extension of time to file automatically extends the Delaware filing deadline. It does not extend the time to pay. Interest and penalties continue to accrue from the original due date on any unpaid balance.¹² The Director of Revenue can grant separate extensions of time to pay, including for individual installments, but that relief is discretionary and may require a bond of up to twice the tax involved.¹³

Coordinating With Federal Payments

If you owe Delaware quarterly payments, you very likely owe federal ones too. The IRS requires estimated payments when you expect to owe at least $1,000 in federal tax after withholding and refundable credits, and expect those to cover less than the smaller of 90% of the current year’s tax or 100% of last year’s (110% if prior-year AGI exceeded $150,000).⁷

Federal quarterly deadlines for calendar-year filers are April 15, June 15, September 15, and January 15 of the following year, shifting to the next business day when they fall on a weekend or holiday.³¹⁴ The Q2, Q3, and Q4 dates match Delaware’s; only Q1 differs, since Delaware’s first individual installment is April 30 rather than April 15. Two payments, two envelopes, two dates in April.

1
Delaware Division of Revenue. Declaration of Estimated Income Tax for Individuals
2
Delaware Code Online. Delaware Code Title 30 Chapter 19 – Corporate Income Tax
3
Internal Revenue Service. Estimated Tax
4
Division of Revenue – State of Delaware. Filing Corporate Income Tax
5
Division of Revenue – State of Delaware. Tax Rate Changes
6
Delaware Division of Revenue. Delaware Fiduciary Estimated Income Tax Form FID-EST Instructions
7
Internal Revenue Service. Form 1040-ES Estimated Tax for Individuals
8
Delaware Division of Revenue. Delaware Underpayment of Estimated Taxes Form PIT-UND
9
Division of Revenue – State of Delaware. Payment
10
Justia Law. Delaware Code Title 30 Chapter 5 Subchapter III Section 533 – Interest on Underpayment
11
Division of Revenue – State of Delaware. Personal Income Tax FAQs
12
Division of Revenue – State of Delaware. Corporate Income Tax FAQs
13
Delaware Code Online. Delaware Code Title 30 Chapter 5 – Returns and Payment of Tax
14
Internal Revenue Service. When to File