A more thorough explanation:

Trust fund taxes, also known as payroll taxes, are taxes that an employer pays on behalf of their employees. These taxes include Social Security and Medicare taxes, which are deducted from an employee's paycheck. The employer is required to keep both their share and the employee's share of FICA taxes in a trust fund. Later, the employer must periodically pay the taxes from the trust fund to the IRS, usually quarterly.

If a corporation or individual uses this income instead of it remaining in the trust fund, the IRS will give them a trust fund recovery penalty. This penalty is equal to the taxes withheld. For example, if XYZ Co. misused $10,000 of withheld taxes, the company would have to pay back the $10,000 plus a $10,000 penalty.

For instance, if an employer withholds $100 from an employee's paycheck for Social Security and Medicare taxes, the employer must also contribute $100 to the trust fund. The employer must then pay the $200 to the IRS from the trust fund. If the employer uses the $200 for other purposes, they will be subject to a trust fund recovery penalty.