First you must be eligible- your corporation must be domestic, have 100 or fewer shareholders, have owners who are individuals, estates or exempt organizations, and have not have any resident alien shareholders. There some other devils in the details, but 99% of the LLCs out there qualify.
Second, Form 2553 must be filed with the IRS. It is typically due during the tax year, however, there is relief for the late filing of Form 2553 and we can guide you through that. Generally speaking, to obtain relief with a late S-Corp election, we prepare and file Form 1120S (corporate tax return) and attach Form 2553 to it. The S-Corp tax return cannot be accepted until Form 2553 is processed and approved.
Of course we can take care of all this paperwork for you!