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September 2023 Business 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).

Weekends & Holidays:

If a due date falls on a Saturday, Sunday or legal holiday, the due date is automatically extended until the next business day that is not itself a legal holiday. 

Disaster Area Extensions:

Please note that when a geographical area is designated as a disaster area, due dates will be extended. For more information whether an area has been designated a disaster area and the filing extension dates visit the following websites:

FEMA: https://www.fema.gov/disaster/declarations
IRS: https://www.irs.gov/newsroom/tax-relief-in-disaster-situations

For example, disaster-area taxpayers in most of California and parts of Alabama and Georgia now have until Oct. 16, 2023, to file various federal individual and business tax returns and make tax payments.

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