SEPTEMBER

Tuesday, September 15

Personal. Pay the third installment of your 2015 estimated tax.

Corporations. If you received a six-month extension from March 15, send in your 2014 calendar-year income tax return (Form 1120 or 1120-A) and pay any tax that is due. Also, pay the third installment of your 2015 estimated income tax.

S corporations. If you received a six-month extension from March 15, send in your 2014 calendar-year income tax return (Form 1120-S).

Partnerships (and LLCs treated as partnerships). File your 2014 calendar-year return if you received a five-month extension from April 15. Provide each partner with a copy of Schedule K-1 (Form 1065).

Employers. August 2015 payroll tax deposit is due if you’re not on a semiweekly deposit schedule.

OCTOBER

Thursday, Oct. 15

Personal. File Form 1040 for 2014 and pay the tax that is due if you received an extension from April 15. This is also the last day to make Keogh or SEP contributions for 2014 if you received an extension.

Employers. September 2015 payroll tax deposit is due if you’re not on a semiweekly deposit schedule.

NOVEMBER

Monday, November 2

Employers. File Form 941 (payroll tax) for the third quarter of 2015 and deposit unpaid taxes. Deposit unemployment tax for the third quarter of 2015 if you owe more than $500 in FUTA for the year.

Employers. During November, ask your employees whose withholding allowances will change in 2016 to fill out a new Form W-4. Also, ask each eligible employee who wants to receive advance payments of the earned income credit during 2016 to fill out a Form W-5.

Monday, Nov. 16

Employers. October 2015 payroll tax deposit is due if you’re not on a semiweekly deposit schedule.

DECEMBER

Tuesday, Dec. 15

Corporations. Pay the fourth installment of your 2015 estimated income tax.

Employers. November 2015 payroll tax deposit is due if you’re not on a semiweekly deposit schedule.