shall be liable in his own person and estate for payment to the United States of an amount equal to the sum of the taxes required to be deducted and withheld from those wages by the employer under subtitle C of the Code and interest from the due date of the employer's return relating to such taxes for the period in which the wages are paid.
Example. Pursuant to a wage claim of $200, A, a surety company, paid a net amount of $158 to B, an employee of the X Construction Company. This was done in accordance with A's payment bond covering a private construction job on which B was an employee. If X Construction Company fails to make timely payment or deposit of $42.00, the amount of tax required by subtitle C of the Code to be deducted and withheld from, a $200 wage payment to B, A becomes personally liable for $42.00 (i.e., an amount equal to the unpaid taxes), plus interest upon this amount from the due date of X's return.
shall be liable in his own person and estate for payment to the United States of an amount equal to the sum of the taxes which are required by subtitle C of the Code to be deducted and withheld from wages paid on or after January 1, 1967, and which are not paid over to the United States by the employer, and interest from the due date of the employer's return relating to such taxes. However, the liability of the lender, surety, or other person shall not exceed 25 percent of the amount supplied by him for the payment of wages. The preceding sentence and the second sentence of section 3505(b) limit the liability of a lender, surety, or other person arising solely by reason of section 3505, and they do not limit the liability which the lender, surety or other person may incur to the United States as a third-party beneficiary of an agreement between the lender, surety, or other person and the employer. The liability of a lender, surety, or other person does not include penalties imposed on the taxpayer.
26 C.F.R. §31.3505-1