If you are a Corporation or an LLC that is delinquent on 941's and have created a large enough balance to attract the attention of an IRS Revenue Officer, you will eventually be dealing with two different issues: the 941's and the Trust Fund Tax or Form 6672.
By hiring a tax professional like Washington Tax Services, our focus is primarily on making a sure a solution is place to address the 941 taxes. However, if your case does reach the field of the IRS, the IRS Officer will also be focusing on assessing the "Trust Fund" of the 941's against the owners, personally.
The Trust Fund tax as mentioned also in numerous posts below is that portion of the tax which includes what was actually supposed to be withheld from employee's paychecks. By the law, the IRS can assess this portion of the 941 tax against you personally if you are an owner of a Corporation or an LLC (previously LLC were treated as sole proprietors, but the law changed in the beginning of 2009). The Trust Fund usually comprises about 55% of the 941 tax.
The good news is if we represent you on your 941 issue and offer a livable payment agreement on the 941 taxes, we can also get the IRS to postpone any collection activity of the Trust Fund taxes (if they are assessed).