(a) An automatic six-month extension for filing an annual return will be granted if the application for automatic extension (form CT-5) is filed and a properly estimated tax is paid on or before the due date of the return for the taxable period for which the extension is requested. (See section 22-1.3 of this Title Properly estimated tax.) Failure to meet the requirements of this subdivision will make the application invalid, and any return filed after the due date will be treated as a late-filed return.

(b) An automatic six-month extension for filing a combined return will be granted to a group of corporations authorized to file a combined return if the application for automatic extension (form CT-5) is filed and a properly estimated tax is paid on or before the due date of the return for the taxable period for which the extension is requested. (See section 22-1.3 of this Title Properly estimated tax.) Failure to meet the requirements of this subdivision will make the application invalid, and any return filed after the due date will be treated as a late-filed return. To obtain an automatic extension, an application must be filed by the corporation paying the tax for the combined group. The applicant must submit the following information:

The corporation paying the tax for the combined group must pay with the application the properly estimated combined tax plus $250, as provided in section 18-6.2 of this Title, for each of the taxpayers included in the combined group.

(c) On or before the expiration of the automatic six-month extension, the Tax Commission may grant additional three-month extensions of time for filing returns when good cause exists. Up to two additional three-month extensions of time for filing returns for any taxable year may be granted when good cause exists. An application for each additional three-month extension must be made in writing before the expiration of the previous extension. Additional extensions of time for filing by a combined group must be requested in one application by the corporation paying the tax for the combined group. The applicant must submit the following information:

(d) Any extension of time for filing a return granted under this Subpart will not extend the time for the payment of any tax due. (However, see section 22-1.2 of this Title for extensions of time for payment of tax. Also see section 2392.1 of this Title for provisions relating to the existence of reasonable cause for purposes of not imposing the addition to tax for failure to pay the amount of tax shown on a return where there are valid extensions of time to file.)