(1) The Department may, upon proper cause shown, grant a taxpayer an extension of not more than 60 days for the filing of any tax return. Application for such extension shall be made on or before the last day for the payment of the tax, in such form as the Department prescribes.

(2) If any Federal taxing authority grants to any taxpayer an extension for the filing of Federal income tax returns for a period in excess of 60 days, the Department may grant an additional extension of time for the filing of any tax returns affected thereby, not to exceed the date of termination of the Federal extension period.

(3) In order for an extension to be granted, the taxpayer must file a tentative return and pay 100% of the tax estimated to be due, on or before the statutory due date. The extension will not relieve the taxpayer from the obligation to pay interest and penalty from the date such return was originally due upon the amount of tax due in excess of the estimated tax paid.