Here are important tax due dates in chronological order.
January 15: Deadline to pay the fourth-quarter estimated tax payment
January 31: Deadline for employers to mail out W-2 Forms to their employees and for businesses to furnish 1099 Forms reporting non-employee compensation, interest, and rent paid.
January 31: Deadline for financial institutions to mail out Form 1099-B relating to sales of stock, bonds, or mutual funds through a brokerage account, Form 1099-S relating to real estate transactions; and Form 1099-MISC.
March 1: Deadline for farmers and fishermen to file individual income tax returns unless they paid estimated tax payments.
March 15: Deadline for corporate tax returns (Forms 1120-S), or to request an automatic six-month extension of time to file (Form 7004) for corporations that use the calendar year as their tax year, and for filing partnership tax returns (Form 1065) or to request an automatic six-month extension of time to file (Form 7004)
April 15: Deadline for first quarter estimated tax payments
April 15: Deadline to file individual tax returns (Form 1040) or to request an automatic extension (Form 4868) for an extra six months to file your return, and for payment of any tax due. Deadline for corporate tax returns (Forms 1120), or to request an automatic six-month extension of time to file (Form 7004) for corporations that use the calendar year as their tax year
June 15: Deadline for second-quarter estimated tax payments
September 15: Deadline for third-quarter estimated tax payments
September 15, 2021: Final deadline to file partnership and S corporation tax returns, if an extension was requested (Forms 1065 and 1120-S)
October 15, 2021: Final extended deadline to file individual and corporate tax returns (Form 1040 and Form 1120)