[ChemicalWarfare]

>> but has a delay for clearing...

not only is there an ODFI-clearing house - RDFI delay caused by the actual "clearing" process - the whole flow starting from the merchant->payment processor step is a sequence of nightly batches with cutoff times factored in to boot.

from the merchant perspective, however, ACH payment is cheaper to process than a credit card payment and is way less likely to end up in a chargeback.

[doomlaser]

debit card transactions are all ACH then?

[jacobolus]

No. ACH is the digital equivalent of depositing a paper check. The debit networks are what you use to withdraw money from an ATM, and require entering a PIN, but most debit cards nowadays can also operate through credit card networks.

[ChemicalWarfare]

debit cards(not to be confused with bank cards) are closer to credit cards than ACH. in some cases - for example "signature debit" vs "pin debit" - just about identical from the flow perspective.

which is why you can use debit cards in most situations where you would use a credit card where instant check of funds availability and hold is required - e.g. hotel incidentals etc.