Budget billing period calculation

Hi Experts,

We have a below situation -

The end period date on portion for periodic bill is 30.09.2013

However while billing , the end of period is changed ( in EA00 ) as 20.06.2013

So for next period budget billing plan is calculated with start of BBP - 01.10.2013 to 30.09.2014

But since the end of billing period is changed to 20.06.2013 , the BBP amounts are calculated considering time period as from 21.06.2013 to 30.09.2014

which is now greater than 365 days.

This leads to incorrect BBP calculation.

any suggestion how to correct it ? or is this standard SAP functionality ?

Thanks in advance !

Regards,

Nachiket