This bill amends the Internal Revenue Code of 1986 to establish clear procedures for attributing errors in payroll taxes when a third-party payor is involved. It permits these payors to rely on certifications provided by employers, unless the payor possesses constructive knowledge of an error within that certification. The legislation outlines specific liability rules: if a third-party payor has constructive knowledge of an error, both the employer and the payor share responsibility, with the payor's liability limited to the portion they knew was erroneous. However, if the third-party payor lacks constructive knowledge, the employer bears sole responsibility for any resulting liability, which includes amounts due, interest, and penalties. The bill also prevents the Secretary from delaying payroll tax credit processing or auditing an employer solely due to an erroneous return filed by a third-party payor on behalf of a different employer. Furthermore, the bill defines constructive knowledge and provides a safe harbor for third-party payors regarding payroll tax credits. A payor is deemed not to have constructive knowledge if they accurately reported the credit based on employer certification and verified the aggregate wages used to establish the credit amount. This aims to protect third-party payors who act in good faith while ensuring accountability for errors.