September 1
- Labor Day
September 10
- Employees who work for tips – If you received $20 or more in tips during August, report them to your employer.
September 15
- Social security, Medicare and withheld income tax – If the monthly deposit rule applies, deposit the tax for payments made in August.
- Nonpayroll withholding – If the monthly deposit rule applies, deposit the tax for payments made in August.
- Individuals – Make a payment of your 2025 estimated tax if you’re not paying your income tax for the year through withholding (or won’t pay enought in tax that way). Use Form 1040-ES. This is the third instalment date for estimated tax in 2025.
- Partnerships – File a 2024 calendar year return (Form 1065). This due date applies only if you timely requested an automatic 6-month extension.
- S Corporations – File a 2024 calendar year income tax return (Form 1120-S) and pay any tax, interest and penalties due. This due date only applies if you timely requested an automatic 6-month extension of time to file the return.
- Corporations – Deposit the third installment of estimated income tax for 2025.
