If the company would like to use a temporary agency to bring onboard an employee to work for a period of time (3 to 8 months), whose responsibility is it to make sure that the temporary employee is offered health insurance benefits?
The company or the temporary agency for where the temporary employee is hired?
For some purposes of the ACA a temp agency and the client may be a joint-employer. A joint or primary employer must comply with the employer mandate. If the temp agency already offers coverage then the employee would most likely not switch off that to the other employer. An employer only owes the fee if the employee gets Marketplace subsidies. So given this a safe-bet would be to simply offer the temp employee coverage. We haven't found a specific rule that makes not offering coverage a safe bet in this sort of situation. You can read more unofficial advice about the matter here.