Generally, a corportion must file an 1120 even if there is no income to report. However, there are special circumstances and exceptions. See the citaton below and the rest of the instructions for Form 1120 at:
http://www.irs.gov/pub/irs-pdf/i1120.pdf
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Who Must File
Unless exempt under section 501, all domestic corporations (including corporations in bankruptcy) must file an income tax return whether or not they have taxable income. Domestic corporations must file Form 1120, unless they are required, or elect to file a special return. See Special Returns for Certain Organizations, below."