I just finished a mortgage compliance audit so I can answer this one. Look at 202.13(b). "The applicants shall be asked but not required to supply the requested information. If the applicant chooses not to provide the information or any part of it, that fact shall be noted on the form. The creditor should also note on the form, to the extent possible, the ethnicity, race, and sex of the applicants on the basis of visual observation and surname."
If the customer has been with the Bank for 10 years you are obviously familiar with him/her. I would note on the application that the customer did not provide the information and note that the Bank provided it, to the extent possible.
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With the lights out, it's less dangerous.