File a 2018 calendar year income tax return (Form 1120S) and pay any tax due. Provide each shareholder with a copy of Schedule K-1 (Form 1120S), Shareholder's Share of Income, Deductions, Credits, etc., or a substitute Schedule K-1. If you want an automatic 6-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.
S corporation election. File Form 2553, Election by a Small Business Corporation, to elect to be treated as an S corporation beginning with calendar year 2019. If Form 2553 is filed late, S treatment will begin with calendar year 2020.
File a 2018 calendar year income tax return (Form 1120S) and pay any tax due. This due date applies only if you timely requested an automatic 6-month extension. Otherwise, see March 15. Provide each shareholder with a copy of Schedule K-1 (Form 1120S) or a substitute Schedule K-1.
If you operate on a fiscal year, see tax calendar information for Fiscal-Year Taxpayers.
September 2 — Everyone
Federal Holiday (Labor Day) Details
September 10 — Employees who work for tips
If you received $20 or more in tips during August, report them to your employer Details
September 15 — Individuals
Make a payment of your 2019 estimated tax if you are not paying your income tax for the year through withholding (or will not pay in enough tax that way). Use Form 1040-ES. This is the third installment Details
September 15 — S Corporations
File a 2018 calendar year income tax return (Form 1120S) and pay any tax due. This due date applies only if you timely requested an automatic 5-month extension Details
September 15 — Partnerships
File a 2018 calendar year return (Form 1065). This due date applies only if you were given an additional 5-month extension Details
September 15 — Corporations
Deposit the third installment of estimated income tax for 2018 Details
September 15 — Social security, Medicare, and withheld income tax
If the monthly deposit rule applies, deposit the tax for payments in August.