Applicability of service tax

If you are registered under section 12AA of the Income Tax Act, 1961 and doing specified "charitable activities" you shall be exempt under the Mega Notification Exemption. Otherwise, liable to pay service tax.

For the second part of your query, you needed to pay service tax on the mentioned services (manpower supply and security) under the Reverse Charge Mechanism at the rate of 75% (i.e. 9.27%) of the value till 31.03.15, which has been changed to 100% of the taxable value (i.e. 12.36% till 31.05.15 and 14% w.e.f. 01.06.15).