Hi Joanna,
this can be caused with using in "Further selections" the flag button Nat.Crcy Instead of Local Crcy.
In case the postings are in other than local currency.
Please try it and check how the amounts looks after test run with and without this flag.
If you are speaking about reverse charge tax ( with ESA/ESE ), customize report via FISKVC_TAXSECTN ( sm34 ) where by combination of document type and relevant reverse charge tax code is mentioned transaction type only ESA. You should not report both of them ( ESA/ESE ). Relevant for this report is only transaction type ESA as this contain relevant tax amount.
Jan