Stax return & actual paid difference - help

Dear Friends, 

I need some help on how to file the service tax return. As you all know march ending happened and lots of back dated entries are done by organisations, to adjust the expenditure. But on 31/03/15 we had to pay service tax and as on 31/3/15 the following was the information as per books of accounts:

stax payable: 100/- 

cenvat avl : 50/- 

Hence we paid Rs.50/- stax in cash on 31/3/15 after availing cenvat of Rs.50/- 

But today while calculating the return data the service tax data had changed due to entering of back dated entries and the revised stax details are as below: 

stax payable : 200/- 

Cevnat avl: 180/- 

But as per data on 31/3/15 we have actually paid cash rs. 50/- so now what should be my entry shall i avail cenvat 150 , and pay the cash rs.50/- (already paid) and keep remaining balance of 180-150=  30 as cenvat closing balance.

or 

shall i avail full cenvat credit of rs.180/- and in return show rs.20/- as stax for march 15 & Rs.30/- as advance tax. 

Please clarify my doubt.