>There are various ACH systems around the world. The World Bank identified 87 systems in their 2010 Survey
Seems to me like there are many different ACH systems, but perhaps the one referred to colloquially as ACH is specifically FedACH, the American system.
ACH is a US-centric term that seems to be used for both the general concept of netted/batched customer-facing interbank transfers, as well as the US-specific set of agreements, rules, participants, and regulating body that together implement one such network.
There are many national and international equivalents, but the linked Wikipedia page gets many of the examples pretty wrong, listing e.g. card acquirers/processors and central banks as examples for other such networks.
Direct equivalents would e.g. be SEPA Credit Transfer (but not SEPA Instant) and SEPA Direct Debit in the Eurozone or FPS (credit push only) in the UK.
> Seems to me like there are many different ACH systems, but perhaps the one referred to colloquially as ACH is specifically FedACH, the American system.
Giro might be the other, possibly broader term for something similar:
Moreover, not even overseas transfer exists in the "ACH sense". Money is moved between ledgers of the same currency so what you will have is a correspondent bank holding your position in that currency.
It still Nacha which is a US institution as you mention. However, I don't see how that protects in the case of a fraudulent overseas transaction. What recourse do you have if an overseas bad actor tricks you into sending money to his overseas account via international ACH?
I worked for a NACHA processing backend for some years, the mechanism of protecting overseas transactions from bad actors is usually based on sending additional information contained in the IAT transaction, which includes some extra data from both the origination and the receiver[1]. When the bank process it, it could either:
1) settle the transaction in the next few days (3 usually).
2) ask for additional information on the next few days.
3) deny (return) the transaction if it looks too suspicious according to the bank.
What if an overseas bank just claims they didn't receive your transfer when they did?
Others have covered the overseas part, but for the bank claims they didn't receive you're transfer part, I would expect that to show up on the settlement process. If there is a disagreement between banks, when they later check how much each bank owes each other, there should be a discrepancy the banks need to work out.
Note: not an expert in how ACH works or how settlement is done.
Usually there's a 3 day window for the money to settle, if the bank claims that it did not receive the transaction on this time window, they will "deny" the failed transaction and send to the originator a "return"[1] which contains the type and explanation of why did it failed, and the money won't be transferred to the receiver.
If it surpass the 3 day window a "late return" will be sent to notify the origination that the transaction failed, however, the money may already have been transferred to the receiver.
IATs are a pretty niche thing, but I think they're still to a correspondent bank in the US. Not common, and most banks won't allow you to originate them without special arrangement.
