When Is a Corporate Tax Return Due?

Most people are aware of the traditional April 15 Internal Revenue Service tax return deadline for filing personal tax returns. However, business owners may face different due dates for other tax documents, including corporate tax returns. Perhaps perceived differences between C corporations and S corporations trigger questions about when returns are due. Uncertainty about fiscal tax years that do not coincide with calendar years also can lead to confusion.

C corporations using the calendar year as their fiscal year must file their income tax return, Form 1120, by March 15. Corporations can request and receive an automatic six-month filing extension by filing Form 7004 by this date. C corporations must pay any tax due at this time. If a C corporation requests an extension, it must pay what it estimate it owes at the time it submits the extension request.

S corporations using the calendar year as their fiscal year must file Form 1120S by March 15. S corporations must provide each shareholder with a copy of Schedule K-1, "Shareholder's Share of Income, Deductions, Credits," by this date unless requesting the extension.

Shareholders must pay their proportionate share of any tax due at this time. S corporations can also request and receive an automatic six-month filing extension by filing Form 7004 by March 15. Shareholders should pay their proportionate share of any estimated taxes due at the time of the extension filing.

Both Form 1120 and Form 1120S are due on the 15th day of the third month following the end of the corporation's tax year. For example, corporations with a fiscal year ending March 31 must file their tax returns by June 15. Corporations whose fiscal year ends June 30 must file by September 15; fiscal years ending September 30, by December 15. Any tax due must be paid at this time.

S corporations must provide each shareholder with a copy of Schedule K-1 by the date of the tax return deadline. As with calendar tax years, C corporations and S corporations can file Form 7004 by the due date and receive an automatic filing extension of up to six months. A C corporation must remit the estimated tax due at that time. An S corporation can remit payment directly or have the shareholders remit their proportionate share of the estimated tax at that time.

If an S corporation pays its taxes directly to the IRS with a company check, that tax payment will be treated as a distribution. The amount of the check will be proportionately allocated to each shareholder as a reduction in income from the S corporation.