In payroll, semi-monthly means employees are paid twice per month, which differs from biweekly pay. A semi-monthly schedule results in 24 total payments a year. Common dates include the 15th and 30th/31st of each month. The exact day of the week varies, which may affect employee planning. Semi-monthly is generally used for salaried employees where monthly deductions like insurance, taxes, and retirement contributions are easier to manage evenly.