Estimated tax requirements for corporations
Estimated tax requirements have changed for some corporations.
The information below explains the new rules that apply to tax years beginning on or after January 1, 2026.
Estimated tax is the amount of tax (after credits) that a corporation expects to owe for the current year.
Corporations may need to make estimated tax payments during the year. These payments can include a mandatory first installment (MFI) and quarterly installments of estimated tax.
Corporations that are subject to the MTA surcharge must also calculate and pay estimated tax for the surcharge when making these payments.
When payments are required
Most corporations must make:
- an MFI if their tax after credits from two years earlier is at or above the threshold amount below.
- quarterly estimated tax payments if they reasonably expect their tax after credits for the current year to be at or above the threshold amount below.
Threshold amounts
- For C corporations taxable under Article 9-A, the threshold is $5,000.
- For S corporations taxable under Article 9-A, no estimated tax payments are required.
- For other corporations, the threshold is $1,000.
How and when to make payments
Most corporations must e-file Form CT-300 and CT-400. For details, see:
- Form CT-300, Mandatory First Installment of Estimated Tax
- Form CT-400, Estimated Tax for Corporations
For information on payment due dates for the current year, visit 2026 tax filing dates.
For more information
- Corporation tax estimated tax forms and instructions (current year) or (prior years and periods)
- Verification requirements for e-file
- Frequently asked questions about Form CT-300
Updated: