March 11 – Individuals – Report February tip income of $20 or more to employers (Form 4070).

March 15 – Calendar-year S corporations – File a 2023 income tax return (Form 1120-S) and provide each shareholder with a copy of Schedule K-1 (Form 1120S) or a substitute Schedule K-1 — or file for an automatic six-month extension (Form 7004). Pay any tax due.

March 15 – Calendar-year partnerships – File a 2023 income tax return (Form 1065 or Form 1065-B) and provide each partner with a copy of Schedule K1 (Form 1065) or a substitute Schedule K1 — or request an automatic six-month extension (Form 7004).

March 15 – Employers – Deposit Social Security, Medicare and withheld income taxes for February if the monthly deposit rule applies

March 15 – Employers – Deposit nonpayroll withheld income tax for February if the monthly deposit rule applies.

April 1 – Employers – Electronically file 2023 Form 1097, Form 1098, Form 1099 (other than those with an earlier deadline) and Form W-2G

April 10 – Individuals – Report March tip income of $20 or more to employers (Form 4070).

April 15 – Individuals – File a 2023 income tax return (Form 1040 or Form 1040-SR) or file for an automatic six-month extension (Form 4868). (Taxpayers who live outside the United States and Puerto Rico or serve in the military outside these two locations are allowed an automatic two-month extension without requesting an extension.) Pay any tax due.

April 15 – Individuals – Pay the first installment of 2024 estimated taxes (Form 1040-ES) if not paying income tax through withholding or not paying sufficient income tax through withholding.

April 15 – Individuals – Make 2023 contributions to a traditional IRA or Roth IRA (even if a 2023 income tax return extension is filed).

April 15 – Individuals – Make 2023 contributions to a SEP or certain other retirement plans (unless a 2023 income tax return extension is filed).

April 15 – Individuals – File a 2023 gift tax return (Form 709) or file for an automatic six-month extension (Form 8892). Pay any gift tax due. File for an automatic six-month extension (Form 4868) to extend both Form 1040 and Form 709 if no gift tax is due.

April 15 – Household employers – File Schedule H, if wages paid equal $2,600 or more in 2023 and Form 1040 isn’t required to be filed. For those filing Form 1040, Schedule H is to be submitted with the return so is extended if the return is extended.