According to IS-IDEC record structure, the various VAT fields therein are not only for classification reasons, but will rather form amongst other fields such as gross, tax etc. the net billing amount.
Based on this, in case an airline decides to seperately debit for VAT on fare in the IS-IDEC, on the same time the fare gross amount actually needs to be reduced by that very VAT amount.
This leads to the problem, that prorate is done on the gross fare amount and incorrect rejections may occur, it even may more often happen, that a billing will be erroneously accepted as the billed amount is reduced by VAT.
To make a correct evaluation, the billed airline needs to sum up the gross value with the VAT value billed by the other carrier.
Carrier A billing
USD 100 gross fare
USD 10 VAT on fare
Carrier B needs to add USD 10 to USD 100 to have a correct rejection basis.
Carrier B reports in IS-IDEC USD 110 as gross fare whereas original billing amount is USD 100 gross fare.
Question: Is there any problem with IATA validation, as the rejection data doesn't match the originally billed gross amount as well as VAT amount?