Think of it this way: the member might have a negative balance limit, but Reg. E says you aren’t allowed to charge them a fee for dipping into it unless they specifically opt in for that level of service. But this rule of thumb ONLY applies to ATM and everyday debit card transactions, NOT to checks and ACH items, nor to recurring debit transactions.
Since debit card transactions that have been authorized and come through to CU*BASE for posting cannot be returned like a check or ACH item, when CU*BASE receives the transaction we have no choice but to post it. Reg. E says you can only charge the member your fee if they said it was okay to do so. If you want to avoid authorizing transactions where the member doesn’t have the money, you might want to verify whether or not you are including your ANR limits in your authorization balances. But remember that in any case, a lot can happen between the time a member makes an authorized debit card purchase and when it finally hits his account.