Maybe I'm overthinking it and I can do an intercompany JE from Company A expense account to Company B expense account, and then do a credit memo on Company B to the same expense account.

That is an accounting question, not a system question.  Talk to your CPA for advice on the proper transaction trail (which auditors would like).

Thanks. The question was meant more to the functionality of Sage and the options available within AP.  Perhaps I should have worded it differently.  

Sage 100 does not have any inter-company features, without an enhancement. 

Generally speaking, each Sage 100 company code represents a legal entity and the module / GL data in that company code needs to be a complete story of transactions related to that company.  If you have posted bad transactions of any kind, you have to post reversals / corrections.  Posted transactions can never be deleted (as a core feature of how Sage 100 works).

As a non-accountant, if you have posted transactions in Company A, that do not apply to Company A, I expect you will want to post proper full reversals / corrections in Company A (according to CPA advice).

Thanks for confirming my thoughts on the lack of any inter-company ability, and that posted transactions cannot be deleted.   Much appreciated.   I may have to look into what Sage product do have such functionality beyond Sage 100.