After submitting my personal returns to federal and state, I received an assessment from the state showing I owe a lot of $$$ and showing taxes withheld for 2012 as $0. I then checked my W2 which shows taxes withheld however I noticed a mistake in that my ss# was off by 1 digit.

I know I have to inform my employer and have him issue me a corrected W2C but do I send that to the IRS premptively? The W2C form online that I viewed seems to ask for it to be mailed to the SSA.

You need to contact your company's payroll department to correct your SSN. Your employer will complete a W-2c form, which is a corrected W-2 form. This will be the form you will use to file your yearly income taxes. Your ER needs to complete the top portion of the W-2c if he is only changing the SSN or the name. If he is changing dollar amounts, he will complete the entire W-2c form. Your ER needs to file the W-2c form and a W-3c form with the SSA and give a copy to you. The W-2c and W-3c forms are similar to the original forms sent by your ER.SO, you should have your employer prepare and file Form W-2C (as in "Corrected") to eliminate the wages on the wrong number and add them to the correct one. Your Social Security earnings account won't be credited properly unless this is done. use the W-2C only and contact the SSA to ensure that your earnings were correctly reported. SO as long as If the corrected W-2, W2C, has a change in either box 1 or box 2, you need to file an amended return for the affected tax year since the missing income was reported in box 1, which could result in a higher tax liability for the tax year in question. NOTE:If the new form does change anything that you reported when you filed already, then you must file an amended return.Amended returns have to be paper mailed
You can ensure that your earnings were correctly reported by requesting a Social Security Statement report. This is something you might want to consider doing every few years anyway. You can request your report from the SSA web site.