you have hired a 3rd party company to be your check printer. they will be printing checks on behalf of your customers. of course providing them a listing of customer names and accounts would be beneficial, and business necessary. think about you don't provide and a customer enters their data wrong, there would be no ability for the vendor to verify the data is correct, they would just print and send out.
the bigger question becomes at what frequency you would provide, as your customer base can change daily with new accounts opened and old accounts closed.
your contract should discuss the purpose and use of the account listing.
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