Dear Sir.
As per Rule 4 (a) of Point of Taxation rules, 2011, where taxable service has been provided before the change in effective rate of tax, the point of taxation shall be the date of Invoice or the date of receipt of payment, whichever is ealier.
In your case the taxable Service of Security was provided, before the change of effective rate of tax (effective rate of tax was changed from 01/04/2012 and the service was provided till 31/03/2012), the tax rate applicable on the date on which invoice was prepared. In this case invoice was prepared on 01/04/2012, effective rate of tax 12.36 % would be applicable.
Needless tp refer the date of payment, as it would be received only after 01/04/2012 and you had also mentioned that you would receive payment lateon i.e after the issue of Invoice.
DILIP DARJI.