Regardless of where any sales cash went or the enity type or ownership interest, A was stealing from B. A was able to do this because the bank allowed cash back on business accounts. As a result the bank had to pay all its tellers for the time they spent giving depositions and appearing in court.
Obviously A&B had a poor accounting system. Perhaps A appealed to B's greed by stating we will only record and pay taxes on money deposited to the bank.
Macy