Form NYC-300 is the Mandatory First Installment (MFI) that C corporations subject to the New York City Business Corporation Tax file with the NYC Department of Finance to prepay 25 percent of their estimated current-year tax. It has four lines, it is due by the 15th day of the third month of your tax year (March 15 for calendar-year filers), and you only file it if your tax for the second preceding year exceeded $1,000.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026)
Who Has to File and By When
Every C corporation subject to the NYC Business Corporation Tax under Title 11, Chapter 6, Subchapter 3-A of the Administrative Code must file Form NYC-300 if its tax for the second preceding year exceeded $1,000.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026) “Second preceding year” means two years back. For a 2026 filing, the trigger is your 2024 tax. If that 2024 figure was $1,000 or less after credits, you do not file the NYC-300 at all.
The MFI is due two and a half months after the start of your tax year.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026) Calendar-year filers owe it March 15. Fiscal-year filers count two and a half months from the first day of their fiscal year. If the date falls on a Saturday, Sunday, or legal holiday, it moves to the next business day. There is no extension available for the MFI, even if you later extend your annual return.
One boundary worth naming: S corporations are not subject to the Business Corporation Tax and do not use Form NYC-300. They remain subject to the General Corporation Tax with its own separate first-installment rules.2NYC Department of Finance. Business Corporation Tax
What You Need Before You Open the Form
Two items get you through the form:
- Your Employer Identification Number. It has to appear on both the declaration and the payment so the Department can credit your account.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026)
- Your total tax after credits for the second preceding year. Pull it from the return you filed for that year — typically Form NYC-2, NYC-2.1, NYC-2.2, or NYC-3L depending on your situation.
The blank form is a PDF on the Department of Finance website, and it is also available inside the NYC e-Services portal if you plan to file electronically.
Completing the Four Lines
The whole form:
- Line 1. Enter the total tax after credits from the second preceding year. For a 2026 filing, this is your 2024 figure.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026)
- Line 2. If Line 1 is more than $1,000, multiply it by 25 percent. That is the MFI.
- Line 3. Enter any overpayment from a previously filed return that you want to apply to the MFI. Only use overpayments on returns you have actually filed, not ones you expect to claim.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026)
- Line 4. Line 2 minus Line 3. This is what you pay with the form.
A quick example. Say your 2024 BCT after credits was $20,000. Line 2 is $5,000. You have a $1,200 overpayment sitting on a previously filed return and apply it, so Line 3 is $1,200. Line 4 is $3,800, and that is what you remit.
How to Submit It
Electronic Filing
The Department of Finance pushes electronic filing through its e-Services portal at NYC.gov/eservices.1NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026) You enter the form data, pay in the same session, and get a confirmation number immediately. That confirmation is your proof of timely filing. If you work through a tax professional or approved software, e-filing is available that way too.
Paper Filing
If you file on paper, mail the form and payment to:
NYC Department of Finance
P.O. Box 3929
New York, NY 10008-39291NYC Department of Finance. NYC-300 Mandatory First Installment by Business C Corporations (2026)
Make the check or money order payable to “NYC Department of Finance,” in U.S. dollars drawn on a U.S. bank. Write your EIN on the remittance. Keep a copy of the form and your postal tracking, and watch for the payment to clear.
What Happens After the MFI
The NYC-300 payment is the first installment of your estimated Business Corporation Tax for the year. Any estimated tax beyond that gets paid in installments on Form NYC-400, and when you file the NYC-400 you take credit for both the 25 percent MFI you just paid and any prior-year overpayment you applied.3NYC Department of Finance. NYC-400 Estimated Tax by Business Corporations The NYC-400 installments then cover whatever estimated tax is left.
Penalties for Missing or Underpaying
Miss the deadline or pay too little and you owe an addition to tax under Administrative Code § 11-676. The Department applies interest at the underpayment rate it sets each quarter, running from the installment due date through the 15th day of the third month after the close of the tax year.4Justia Law. New York City Administrative Code ADC011-676 – Additions to Tax and Civil Penalties For the first quarter of 2026 that rate is 11 percent; for the second quarter it is 10 percent.5Department of Finance. Business Interest Rates Interest compounds daily, so a short delay stops being cheap quickly.
You can avoid the underpayment addition by meeting a safe harbor. The common one is paying at least 100 percent of the tax shown on your prior-year return, provided that return covered a full 12 months. An alternative covers 90 percent of the tax ultimately shown on the current year’s return.4Justia Law. New York City Administrative Code ADC011-676 – Additions to Tax and Civil Penalties Paying the straight 25 percent calculation on time is the simplest path through.