Generally, a credit union can take up to 10 business days to determine if an EFT error has occurred. The credit union should respond to you within three business days of completing its investigation.
If the credit union cannot complete its investigation within 10 business days, it may take up to 45 days to determine if an error has occurred. In this case it must provisionally (temporarily) reimburse your account. (Note: Depending on the type of transaction, the 45-day limit can be extended.)