Moving money within a bank is instant because the bank settles instantly, anywhere outside the bank (like the credit card or debtor) has to process through SWIFT, which is slow and takes a couple days. The real conspiracy is why we still use an antiquated SWIFT system. But don't worry, it'll be going away and replaced with something much better soon enough.
Same with ACH. That money moves instantly. New rules were made that went in effect in 2017 that ACHs could be processed same day instead of the 2-3 day wait. I worked on the training for this at a bank. That’s when all the banks started advertising they could pay you two days early like it was some sort of benefit they were offering when in fact they were having to do that to be in compliance. If your bank doesn’t pay you two days early (when they actually receive your money) find one that does. They have the money early. If you don’t get it the bank is sweeping it into overnight investment accounts for two days making money on it.
