September 2023 Business Tax Due Dates
September 15 - S Corporations
File a 2022 calendar year income tax return (Form 1120-S) and pay any tax due. This due date applies only if you requested an automatic 6-month extension. Provide each shareholder with a copy of their Schedule K-1 (Form 1120-S) or a substitute Schedule K-1 and, if applicable, Schedule K-3 (Form 1120-S) or substitute Schedule K-3 (Form 1120-S).
September 15 - Corporations
Deposit the third installment of estimated income tax for 2023 for calendar year
September 15 - Social Security, Medicare and withheld income tax
If the monthly deposit rule applies, deposit the tax for payments in August.
September 15 - Nonpayroll Withholding
If the monthly deposit rule applies, deposit the tax for payments in August.
September 15 - Partnerships
File a 2022 calendar year return (Form 1065). This due date applies only if you were given a 6-month extension. Provide each partner with a copy of their Schedule K-1 (Form 1065) or a substitute Schedule K-1 and, if applicable, Schedule K-3 (Form 1065) or substitute Schedule K-3 (Form 1065).