If you are not going to investigate the "de minimis" claims, you should be crediting the customer within a day of making the decision not to investigate. You don't take 45 days or even 10 days. Your investigation is finalized when you make the decision, and the crediting should take place by the next day.
Of course, you should keep a record of these "fast lane" approvals to identify any customers who decide to "game" your policy (and to show you've resolved the claims).
As for consumers who have also pursued a direct credit with a merchant and receive "unjust enrichment" in what amounts to a double credit, you have the right to pull back the funds from the merchant's credit to your customer's account. "Reversal of duplicate credit from merchant" is an apt description and it is not a reversal of the final credit from the customer's claim against the bank.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8