> ACH payments historically operated on a daily or twice daily batch processing, and they’re (importantly) “negative confirmed.” This means that you do not get

> ACH payments historically operated on a daily or twice daily batch processing, and they’re (importantly) “negative confirmed.” This means that you do not get immediate reliable feedback that an ACH transfer or withdrawal has succeeded. The association’s rules require financial institutions to report errors (via even more batch processing) within 5 business days, and given that errors are expected in the ordinary course (most commonly, insufficient funds, since funds availability is not and cannot be guaranteed at transaction time), businesses and banks have to make decisions on what degree of risk they’re willing to tolerate. A colleague of mine years ago told me a story about check clearing in the "old days". Northern Trust in Chicago handled a large percentage of check clearing for the entire US. Their back office building had a heliport because they had a twice-daily cargo flight from O'Hare filled with all the checks that needed to get cleared. I almost feel like the batch processing was because of the scheduled delivery of the physical checks to these processing centers around the country.