I processed payroll for eight months before realizing I had been miscalculating overtime rates. The error seemed minor until our tax authority audit arrived.
Misclassifying employees as contractors
My biggest mistake involved treating three part-time workers as independent contractors when they should have been employees. The distinction matters because contractors handle their own taxes while employees require tax withholding. Tax authorities examine work schedules, supervision levels, and equipment ownership to determine classification. I paid back taxes plus interest totaling 18 percent of what should have been withheld.
Ignoring supplemental wage tax rates
Bonuses require different tax treatment than regular wages. I applied standard withholding rates to year-end bonuses, which left employees with unexpected tax bills. Supplemental wages often require flat withholding rates or aggregate calculation methods depending on payment timing and amount.
Missing filing deadlines by one day
Electronic filing systems accept submissions until midnight, but I learned that midnight means the tax authority timezone, not mine. A single late quarterly filing generated penalties that exceeded the actual tax owed by a factor of two.
Calculating gross-to-net incorrectly
I subtracted pre-tax deductions after calculating income tax instead of before. This inflated taxable income for six employees across four pay periods. The recalculation process required amended returns and direct communication with affected employees.
Keeping incomplete payroll records
Auditors requested three years of timesheets, pay rate changes, and tax calculation worksheets. I had deleted calculation spreadsheets after processing each pay period, assuming the final numbers were sufficient documentation. Record retention requirements typically span three to seven years depending on document type and jurisdiction.