Hi SKA,
S_P99_41000062 transaction will work ,if material ledger activate in your system. You can use MB5B report where you can get current period and previous period material stock values vs FS10N material GL account values. It will work for only current period ,previous period and previous year only. MB5B is enough for reconcile the FI and MM balances. Or else you can use MC.9 to get inventory valuation & for FI purpose S_ALR_87012277 - G/L Account Balances use this one.
Regards
Mani