September 11 – Employees who work for tips.  If you received $20 or more in tips during August, report them to your employer.  You can use Form 4070.

September 15 – Individuals.  Make a payment of your 2006 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 date for estimated tax in 2006.  For more information, see Publication 505.

Note.  The 3 months that make up each quarter of a fiscal year may be different from those of each calendar quarter, depending on when the fiscal year begins.

Individuals.  Form 1040.  This form is due on the 15th day of the 4th month after the end of your tax year.

Estimated tax payments (Form 1040–ES).  Payments are due on the 15th day of the 4th, 6th, and 9th months of your tax year and on the 15th day of the 1st month after your tax year ends.