Anytime

Employers - Income Tax Withholding. Ask employees whose withholding allowances will be different in 2016 to fill out a new Form W-4. The 2016 revision of Form W-4 will be available on the IRS website by mid-December.

November 2

Employers - Social Security, Medicare, and withheld income tax. File form 941 for the third quarter of 2015. Deposit any undeposited tax. (If your tax liability is less than $2,500, you can pay it in full with a timely filed return.) If you deposited the tax for the quarter in full and on time, you have until November 10 to file the return.

Certain Small Employers - Deposit any undeposited tax if your tax liability is $2,500 or more for 2015 but less than $2,500 for the third quarter.

Employers - Federal Unemployment Tax. Deposit the tax owed through September if more than $500.

November 10

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

Employers - Social Security, Medicare, and withheld income tax. File Form 941 for the third quarter of 2015. This due date applies only if you deposited the tax for the quarter in full and on time.

November 16

Employers - Nonpayroll withholding. If the monthly deposit rule applies, deposit the tax for payments in October.

Employers - Social Security, Medicare, and withheld income tax. If the monthly deposit rule applies, deposit the tax for payments in October.