In the case of trust fund taxes, taxes withheld from another to be remitted to the government, the IRS is merciless in collecting them. Although they are becoming more reasonable, they will attempt to collect back taxes from anyone they can; the board of directors, all officers, the controller or treasurer, the store manager, anyone who could sign checks, etc.. To determine if you could be held liable, ask your self if you could be reasonable expected to have paid the tax or directed the tax to be paid. If the answer is yes (even remotely), you can be held liable. As president of the company, I expect you can be held fully liable for the taxes. I suggest you 1) HAVE THE COMPANY PAY THE TAXES (as president it is unlikely you can avoid personal liability by any other means), and 2) see an attorney skilled in these matters. (Attorneys who have worked with the IRS on similar cases are far more effective then those who have not.)
Also, the IRS is more lenient on collecting the non-trust fund portion of the tax. For example, you or your attorney can ask that they waive the matching portion of the tax as part of the settlement. (Don?t count of them doing this.)
These taxes can?t be discharged even in bankruptcy. Do everything and anything you can to have the taxes paid (by someone else) before you are ask for the money.