"A bank may require tenants to enter into subordination, attornment, and non-disturbance agreements, which protect the bank's interests in the leases by acknowledging the right of the bank to assume the landlord's position if the borrower declares bankruptcy. To ensure that the bank has full knowledge of all provisions of the lease agreements, the bank also should require tenants to sign an estoppel certificate, which is a statement of material facts or conditions that cannot be denied at a later date."
This is from the OCC's Handbook on Commercial Real Estate Lending.
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Opinions are mine not my employer's, and should not be taken as legal advice.