Impact of posting of a Credit Memo from Vendor, on project costs

Dear Experts,

In our client's business, a user has posted a GR for 372986 NOK in 2015. Against which, an IR (invoice receipt) also have been posted for 371626 NOK.

refer attached screen shots.

As a result, payment also have been made to vendor.

Later at the end of 2015, same vendor has sent a credit memo for 223186 NOK in the same year 2015.

GL balance (FBL3N) is ok.

Now in 2016, the user approaches us stating that project A is still displaying costs as 371626 NOK, instead of 148439 (371625 - 223186) NOK.

Projects cost should also come down as business originally paid a less amount than GR but project cost report is still displaying 371626.

Kindly suggest.

Do we need to reverse all those IR and GR and change the PO's price to that amount? So that, thereafter user can post a GR and IR for the same net value.

Thanks in advance.

Regards,

SAPPS