H.R. 3223 modifies tax law to clarify how errors in payroll tax filings are handled when third-party payroll processors—such as payroll companies, professional employer organizations, or tax agents—submit information on behalf of employers. Under the bill, third-party payors are only liable for errors if they knew or should have known about the mistake; otherwise, the employer bears full responsibility for any resulting taxes owed, interest, and penalties. The legislation also protects employers from having their tax credits delayed or audited solely because a third-party processor made an error, and it gives the IRS the authority to request records from third-party payors. The bill applies to all audits and examinations initiated after it becomes law, providing clearer rules for businesses that rely on outside help to manage their payroll tax obligations.