What is the timeframe on employers remitting the participant contributions to be deposited to their SARSEP accounts? Meaning the participant payroll deductions. Is it 15 days or 30 days?

Neither. Assets must be deposited as soon as they can reasonably be segregated from the employer's general assets, but in all events not later than 15 business days after the end of the month in which the payroll deduction is made. [DOL Reg Sec 2510.3-102]