Your proof of payment stamp needs to reflect the time and date of payment, and payment includes an authorization to charge an on-us account (as discussed above). If the transfer doesn't take place, you aren't entitled to the fees or any other part of the charge to the account. The regulation doesn't address damages for not following through. But I can envision a case in which a Sender tries to sue you for not completing a transfer you charged him for, with the result that he suffered some kind of monetary loss.
If the debit to the account doesn't hit for a few hours, you could find yourself trying to overdraw an account if there's been a debit that's snuck in before you (think an ATM withdrawal or POS transaction, or maybe a check payable to a third party who came in to cash it). For those reasons, I recommend placing a hold on the account for the amount of the charge, to be released when the debit is processed.
If the wire is delayed, there could be a currency conversion rate change that will force you to pay more than you have the authorization to collect from the account. Or the delay could result in late arrival of the funds, which can cost the service provider (your bank) a penalty.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8