I formed a Delaware LLC on November last year, and soon I found that the c-corp is more suitable for my situation, so I decided to dissolve this LLC, it has been dissolved on December last year (submitted formal termination request to Delaware, paid termination fee, and get approved). This LLC has an EIN, but I never opened an account for it, also no income involved. So do I need to report this LLC on my tax return?
If the business had no income then most likely you do not need to file. It may be to your benefit to file however in that you had a loss. The fees you paid to Delaware should be deductible business expenses.
Definitely. What do you mean you dissolved it? Both creating and ending any business form is a formal legal and tax matter. Your LLC is not dissolved if you haven't done anything formally to terminate it. In many states you need to get permission to even end it. Check with the Secretary of State or whereever you formed your llc.
BTW, now you will have to file a tax return for 2011 and also for 2012.