WEB should only be used for consumer accounts, not commercial accounts, so I don't believe the above is correct. First, your core should be set that you don't accept consumer SEC codes on commercial accounts. Second, and the bad news, is that I don't think you can return under the "60-day" window, as that is for consumer accounts, and you clearly state this is a commercial account. Return periods don't "hinge" on the SEC code, they are structured on the type of account that is used.
It certainly wouldn't hurt to contact the ODFI and let them know that you received a WEB transaction to a commercial account and ask for permission to return it. If they deny, you can always tell them you'll be filing a rules violation reprot on the transaction. But make sure you also get your core in order so this doesn't happen again.
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