September 5 — 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 — Partnerships
File a 2017 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 2017 Details
Oct 31 Social security, Medicare & withheld income tax.
File Form 941 for 3rd quarter. Deposit/pay any undeposited tax under the accuracy of deposit rules .If your tax liability is less than $2,500, you can pay it in full w/timely filed return.
October 31 — Certain small employers
Deposit any undeposited tax if your tax liability is $2,500 or more for 2017 but less than $2,500 for the third quarter.
October 31 — Federal unemployment tax
Deposit the tax owed through 09-if more than $500.