We here at Optic try to take the stress out of filing taxes.

We created this 2025 Tax Deadline Calendar for Startups – C-Corps, Partnerships and S-Corps – so you can stay on top of your filing requirements this year!

We can’t change the tax deadlines, but we can arm you with what you need to make sure you never miss another deadline!

‍Last Updated Monday, January 6th, 2025

2025 Tax deadlines

January 31 – Payments for employees and independent contractors

•            1099-NEC
•            1099-MISC
•            1099-K
•            W-2& W-3

February 1 (OpticTax Deadline) Opt-out deadline Federal & State returns extension:

• Extensions are recommended to be filed each year due to the $25,000 penalty risk for missed Form 5472 foreign investment information.
• Extensions are also recommended to allow for a bigger window to make corrections as an “originally filed” tax return through date of extension, that allows for more credits and deductions than amended tax returns.
• We automatically file extensions for returning clients, so we ask you to notify us by February 1st if you don’t want an extension filed.

February 24 (OpticTax Deadline) Submission of Documents for Partnership March deadline

• Optic deadline to receive financials to file for partnership & S-Corp deadline of March 17th, 2025.

February 28 – Paper Information Return Filings Due

• 1099-DIV

March 1 – Delaware Franchise Annual Report & Tax Due for Corporations

●       Calculated by shares issued & assets at year end.

March 15 – S-Corp and Partnership Extensions Due

File an extension to avoid penalties per-partner, per month basis. Please note that the IRS has been assessing penalties on late 8805s & 1042 for dividends and owner payouts. These returns or extensions are due:

• 1065- Partnerships
• 8805 – Partnerships – Income share for foreign partners
• 1120-S – S-Corps
• 1042-S – Corporations – dividends paid to foreign shareholders

March 15 – C-Corp and S-Corp Elections

Must be filed within 75 days of start of tax year.  Benefits foreign-owned LLC members to be taxed as a C-Corp.  US C-Corp shareholders can save taxes as an S-Corp.

• Form 8832 – LLC Election
• Form 2553 – S-Corp Election

March 24 (OpticTax Deadline)

           Submission of Tax Documents to Make April Deadline

If taxes are owed this year, financials must be sent to us by this date to calculate taxes to prevent penalties.

March 31 – eFiling deadline – Deadline for most payout information returns.

           1097, 1098, 1099s – Excluding NEC, 3921, 3922, W-2G

April 14 (OpticTax Deadline)

           Extension for filing Federal & State returns. State Extension Can be Filed by request

April 15 – Tax day Extension Due Date

           1120- C-Corp

           1040- Single Owner LLC, & Individual

           Q1 Estimated Tax Payments Due

Please note that corporations are required to pay estimated taxes on their first year of being profitable.

June 1 – LLC DE Franchise Annual Fee due

June 16 – Q2 Estimated Tax Payments Due

August 25 (OpticTax Deadline)

           Extension Deadline for Signup for Extended Returns

●       Final deadline to sign up for our clean-up bookkeeping for the prior tax year.

September 15 – Final Tax Deadline for Partnerships and S-Corps

Deadline to file Partnership and S-corp returns on 6-month extension deadline

• 1065 – Partnership & MMLLC
• 1120-S – S-Corp
• Q3 Estimated Tax Payments Due
• 1120 – Extension & Returns Due for 6/30 fiscal year-end businesses 

September 22 (Optic Tax Deadline)

• Optic Tax’s final deadline to give us documents in order to guarantee completion by Oct 15th corporate deadline

October 15 – Extended Returns Due

Final deadline for those on 6-month extension. Drop dead date after which penalties will be assessed.

• 1120 – C-Corp
• 1040 – Single Owner LLC, & Individual

December 15 – Fourth Quarter Estimated Tax Deadline

Fourth quarter final estimated tax returns for C-Corps are due on December 15th. For individuals, the deadline is January 15th, 2026.

• 1120 – C-Corp

Other Tax Deadlines

Fiscal Deadlines

The standard Federal tax deadline if not using the Dec 31st year end date is 3.5 months after the end of the month where the tax year ends.

One exception- tax years that end in June have a Sept 15th due date. (June 30th is Australia’s year end, so a lot of companies that have their US fiscal year match theirAustralian activities can be affected by this).

Common fiscal years – we also see are March 30th for UK related companies, and January 31st for tech companies that want to emulate Salesforce.

Dissolution: When companies close they use a fiscal year end date for their deadlines after the month they dissolve with the state.

Penalties

$25k for 5472 late-filing (corp inc tax) $10k for 5471, FBAR, 8938 foreign banking, per month penalties partnerships & S-corps, DE late filing both a fee and a %, late-filing fees for corporate tax owed, late payment penalties, state late filing penalties