"Semi-monthly (https://accountingbyte.com/semi-monthly-pay-meaning/)" is defined by a frequency of something that happens twice per month, ideally evenly spaced, for instance on the 15th and last day. Payroll 'indicates that employees are paid 24 times a year versus the 26 times that they get paid bi weekly. A business will find it easier to plan finances around it, and employees will know what to expect for their pay date. It, however, can complicate overtime calculations for hourly workers as the number of work days differs per a pay period.