These linked articles are self explanatory of the importance to identify and avoid fraudulent payroll service providers.
https://www.irs.gov/uac/newsroom/irs-alerts-payroll-and-hr-professionals-to-phishing-scheme-involving-w2s
https://www.irs.gov/uac/examples-of-employment-tax-fraud-investigations-fiscal-year-2017
https://www.irs.gov/uac/examples-of-employment-tax-fraud-investigations-fiscal-year-2016