S-Corporation

State:
Form CT-1040: Connecticut Income Tax Return
You must file a Connecticut resident income tax return if you were a resident for the entire year and if any of the following is true for the 2014 taxable year: • You had Connecticut income tax withheld; • You made estimated tax payments to Connecticut or a payment with Form CT-1040 EXT; • You meet the Gross Income Test; • You had a federal alternative minimum tax liability; or • You are claiming the Connecticut earned income tax credit (CT EITC).

Form CT-1040NR/PY: Non-Resident/ Part-Time Resident - Guide / Form
You must file Form CT-1040NR/PY, Connecticut Nonresident and Part-Year Resident Income Tax Return, if you were a nonresident or part-year resident of Connecticut in 2014 and if any of the following is true for the 2014 taxable year: • You had Connecticut income tax withheld; • You made estimated tax payments to Connecticut or made a payment with Form CT-1040 EXT, Application for Extension of Time to File Connecticut Income Tax Return for Individuals;

Form CT-1041: Connecticut Income Tax Return for Trusts and Estates - Guide / Form
There are many different requirements for filing a Form CT-1041, it differs between resident trust or estate and non-resident trust or estate.
Nonresident trusts or estates that are members of a partnership or S corporation that receive Connecticut-sourced income from pass-through entities, and where the Connecticut income tax was paid on their behalf by the pass-through entity, are required to file Form CT-1041

Form CT-1065/CT-1120SI: Connecticut Composite Income Tax Return
Every PE that does business in Connecticut or has income derived from or connected with sources within Connecticut must file Form CT-1065/CT-1120SI regardless of the amount of its income (loss). The PE must first complete either federal Form 1065, U.S. Return of Partnership Income, or federal Form
1120S, U.S. Income Tax Return for an S corporation. Information on the federal return is needed to complete Form CT-1065/CT-1120SI. An electing large partnership (ELP) that completes federal Form 1065-B, U.S. Return of Income for Electing Large Partnerships, must still use Form CT-1065/CT-1120SI. Connecticut does not conform to the electing large partnership provisions.

Federal:
Tax Forms and Instructions for S-Corporations
In order to become an S corporation, the corporation must submit Form 2553 Election by a Small Business Corporation (PDF) signed by all the shareholders. See the Instructions for Form 2553 (PDF) for all required information and to determine where to file the form.