April 15
Individuals. File a 2018 income tax return and pay any tax due by April 15 (if you live in Maine or Massachusetts, the filing deadline is April 17). If you want an automatic six-month extension of time to file the return, file Form 4868, “Application for Automatic Extension of Time To File U.S. Individual Income Tax Return.” Then, file Form 1040 by October 15.
If you are not paying your 2019 income tax through withholding (or will not pay in enough tax during the year that way), pay the first installment of your 2019 estimated tax. Use Form 1040-ES.
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in March if the monthly deposit rule applies.
Household employers. If you paid cash wages of $2,100 or more in 2018 to a household employee, file Schedule H (Form 1040) with your income tax return and report any household employment taxes. Report any federal unemployment (FUTA) tax on Schedule H if you paid total cash wages of $1,000 or more in any calendar quarter of 2017 or 2018 to household employees. Also, report any income tax you withheld for your household employees.
Corporations. File a 2018 calendar year income tax return (Form 1120) and pay any tax due. If you want an automatic six-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.
Corporations. Deposit the first installment of estimated income tax for 2019.
May 10
Employers. For Social Security, Medicare, and withheld income tax, file Form 941 for the first quarter of 2019. This due date applies only if you deposited the tax for the quarter in full and on time.
May 15
Employers. For Social Security, Medicare, withheld income tax, and nonpayroll withholding, deposit the tax for payments in April if the monthly rule applies.