The 4980H(a) penalty applies when you fail to offer minimum essential coverage to at least 95% of your full-time employees and at least one employee claims a premium tax credit. The penalty is $2,970 per year ($274.50/month) for each full-time employee, excluding the first 30 employees.
For example, if you have 100 full-time employees and don't offer coverage, the penalty would be $2,970 × 70 employees = $207,900 annually (assuming at least one employee takes a subsidy).