October 10

Employees who work for tips – If you received $20 or more in tips during September, report them to your employer. You can use Form 4070.

October 15

Individuals – If you have an automatic 6-month extension to file your income tax return for 2017, file Form 1040, 1040A, or 1040EZ and pay any tax, interest, and penalties due.

Corporations – File a 2017 calendar year income tax return (Form 1120) and pay any tax, interest, and penalties due. This due date applies only if you timely requested an automatic 6-month extension, Otherwise, see April 17, earlier.

Employers Nonpayroll withholding. If the monthly deposit rule applies, deposit the tax for payments in September.

Employers Social Security, Medicare, and withheld income tax. If the monthly deposit rule applies, deposit the tax for payments in September.

October 31

Employers – Social Security, Medicare, and withheld income tax. File form 941 for the third quarter of 2018. Deposit any undeposited tax. (If your tax liability is less than $2,500, you can pay it in full with a timely filed return.) If you deposited the tax for the quarter in full and on time, you have until November 13 to file the return.

Certain Small Employers – Deposit any undeposited tax if your tax liability is $2,500 or more for 2018 but less than $2,500 for the third quarter.

Employers – Federal Unemployment Tax. Deposit the tax owed through September if more than $500.