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The December 15, 2026 Estimated Tax Payment and a Credit Purchase
Published October 28, 2026. For a calendar-year C corporation, the fourth 2026 estimated tax installment is due Tuesday, December 15, 2026 (§6655). A purchased credit can change that payment, but only if the facts support it.
How the installments work
A large corporation generally owes 100% of the required annual payment in four installments of 25%, due on the 15th day of the 4th, 6th, 9th and 12th months (§6655(c)). The December installment is the last. Corporations expecting to owe $500 or more generally need to pay estimates (IRS).
Illustrative arithmetic
Assume a calendar-year C corporation forecasts 2026 regular tax of $4,000,000 and has paid $3,000,000 through September. It signs a transfer agreement for $1,000,000 of credit, which is within its §38(c) capacity of $3,006,250 (0.75 × $4,000,000 + $6,250, TMT assumed zero).
| Item | Without credit | With $1,000,000 credit reflected |
|---|---|---|
| Forecast tax | $4,000,000 | $3,000,000 |
| Paid through September | $3,000,000 | $3,000,000 |
| Remaining (December 15 installment) | $1,000,000 | $0 |
Illustration only. It ignores annualization, other credits, state tax and costs, and assumes the credit is allowed as claimed. The credit price paid is a separate cash cost. See the estimated tax guide for a fuller worked example.
What to document before December 15
- The signed transfer agreement and its date.
- The seller's registration number for the credit property.
- Your credit calculation and the §38(c) memo.
- The estimated tax worksheet showing the effect, and the Form 2220 position.
If the deal will not close by December 15
You can still use the credit on the 2026 return if the transfer is completed inside the payment window; the cost is that the December installment may be paid without the credit benefit. See buying before year end 2026.
Frequently asked questions
When is the December 2026 corporate estimated tax payment due?
December 15, 2026 for calendar-year C corporations (§6655(c)).
Can a purchased credit reduce the December 15 installment?
The IRS Transferability FAQs say a transferee can take a purchased credit into account for estimated tax. Your CPA should confirm that the facts support doing so.
What if I underpay the installment?
You may owe an underpayment penalty computed on Form 2220, unless an exception applies. Talk to your CPA before relying on a credit you have not yet acquired.
Is the credit limited by tax capacity?
Yes. The general business credit cannot exceed the §38(c) limit, and unused credit carries forward under §39.
Owe $50k or more in federal tax?
Tell us your estimated liability and timing. We will show you what transferable credits are available and walk your CPA through the diligence.
Get a tax credit quote §48E buyer guide or call (888) 328-4718
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- FEOC and Prohibited Foreign Entity Rules: What a Tax Credit Buyer Needs to Check
- Buying §45X Advanced Manufacturing Credits: What a Corporate Tax Buyer Should Check
- Marketplace, Broker or Direct From the Seller: How to Buy Transferable Tax Credits
- How Bonus Depreciation and §174A Expensing Change Your Capacity to Use a Purchased Credit
- Buying transferable tax credits