September

Fr 15 Pay the third installment of your 2017 estimated tax – Use Form 1040-ES.

Fr 15 C corporations: Deposit the third installment of your 2017 estimated tax.

Fr 15 S Corporations: File Form 1120-S if you timely requested an extension – see Form 7004

Fr 15 Partnerships: File Form 1065 if you timely requested an extension – see Form 7004

Fr 15 Electing Large Partnerships: File Form 1065-B if you timely requested an extension.

October

Mo 16 C corporations: File calendar year Form 1120 if you timely requested a 6-month extension.

Mo 16 Individuals: File Form 1040, 1040A, or 1040EZ if you timely requested a 6-month extension.

Tu 31 File Form 941 for the third quarter.

Tu 31 Deposit FUTA owed through Sep if more than $500.

November

Mo 13 File Form 941 for the third quarter if you timely deposited all required payments.