Chile Inflation adjustment calcualation were wrong.

we are implementing chile localisation functionality for FA for chile country. but having issue in calcualation.

Example, if an asset purchased on dec-13 and set the date placed as same and set the inflation start date as same dec-2013. but as per system design, asset cannot be revalued in the month of acquired. so no issues. but for jan-2014 month, asset is revalued with some rate which is not correct as per our analysis.

system uses the following formula for calculation = (index value for previous period/index value for period prior to previous  period)-1

if we run revaluation for Jan-14, system taking  December value/november value -1 which is not matching the client requirement. our client is expecting the consider the following values for calculation if we run for Jan-14, system should take  (January/december)-1. so that we can get expected results.