Simple question really that has me slightly confused.
Consider a ledger with two BSVs 01 and 02.
Two legal entities are then assigned to the two BSVs, LE1 to BSV 01 and LE2 to BSV 02.
One operating unit is then assigned to the ledger with default legal context as LE1.
Assign a responsiblity to a user with access to the operating unit (security profile)
Now if i submit an invoice with accounting BSV of 02, how does Oracle determine which LE to stamp
on the transaction while sending it to GL.If it uses the default legal context then it will be wrong.
In addition I see only the OU as an input on most transaction screens not the LE.
Does it determine it using the BSV on the tx?

Ledger 1 (LE1->BS1, LE2->BS2)
OU1->Ledger 1

In R12 you can use one operating unit to serve multiple legal entitites.
While creating an operating unit you define the "default" legal context.
You can pick a different legal entity when entering an invoice. You choose the desired value in "Customer Taxpayer id" field on invoices screen. You can also unhide "Legal Entity" field that is available but hidden (Go to Folders menu and click on Show). This is a ready only field. When you make a selection in customer taxpayer id field the name of the legal entity will automatically appear in "Legal Entity" read only field. Hope that answers your question. There is a similar functionality available in AR.