The amount of Employer NIC you pay will vary depending on the gross salary you pay your employees/directors. The Ember Payroll system will work this out for you automatically and record it in the right categories, so you don't have to.
What's included
The extra bit you pay to HMRC as an employer on top of your gross salaries to the company directors/employees.
What's not included
Payroll adjustments including Student Loan Repayments etc.
How is it taxed?
Your employer NI contributions are treated as a deduction for the company.