Well yeah, but that just makes the business rules even more complex. That makes it more like - reject the transaction if it would move the account balance below zero, unless the account has a flag to allow overdrafts (which is over on the accounts table), in which case we allow the transaction and also enter another transaction for the overdraft fee.
Probably need some more rules like max overdraft amount, max number of transactions etc. I've heard some places may also have the "let's be jerks" rule to reorder transactions to hit overdraft as soon as possible to maximize fees.
Probably need some more rules like max overdraft amount, max number of transactions etc. I've heard some places may also have the "let's be jerks" rule to reorder transactions to hit overdraft as soon as possible to maximize fees.