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 IRS Form 4868, “Application for Automatic Extension of Time To File U.S. Individual Income Tax Return.” Then, file IRS 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 IRS Form 1040-ES.
Employers: For Social Security, Medicare, withheld income tax, and non-payroll 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 (IRS Form 1040) with your income tax return and report any household employment taxes. Report any federal unemployment 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.