If you cashed the check, you can't use the exemption you have for the business, because the transaction isn't transaction in an exemptible account at your institution. So, if you know the transaction is being conducted on behalf of the business, you file using a Part I for the conductor using 2b and a Part I for the business using 2c. It will be reported as a negotiable instrument cashed. No account number will be reported, because an account in your bank was not involved.
But I hope you would refuse the transaction based on the check being drawn on a different bank.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8