Payment of st- old and new scheme

Dear All Hope you are going well...

        A simple doubt confuses me..  As per old scheme of Service Tax, ST is payable on receipt basis and as per new scheme, it is payable on due basis.

One instance-

A provided a taxable service to B for an invoiced amount of 56,180/- (50000+ST @ 12.36) on 25th Jan 2013. 

suppose, B pays 50000 as full settlement in Nov 2013. no more additional payments.

Here as per due basis, A has to pay Rs.6180 as ST irrelevant of receipt from B.

But as per old scheme A have to make back calculation on Rs.50000 (ie, 44500+ ST 5500)

What is your comment.....???