While doing the billing
Check in VKOA with
APPLICATION : V
Condition type : KOFI
Chart of accounts: which is assigned to your company code
account assignment of customer : from billing header
account assignment of material : from billing item level
account key : maintained against your condition types which are relevant for accounting in pricing procedure.
This will give the detail on G/L to which the posting will happen.
Thanks & Regards,
Hegal K Charles
You can also check in tables C00X where X = 1,2,3 etc based on your key combination in VKOA transaction. For ex., G/L mappings on the first key combination would be available in C001 and second would be C002 etc.
You can extract it as pivot excel and analyze it too.