If you are not subject to HMDA and are not an OCC regulated financial institution that is regulated by Part 27 under the Fair Housing Act, then you have to collect monitoring information under Regulation B – ECOA requirements, when applicable.
Regulation B monitoring requirements include collecting Ethnicity, Race, Sex, Marital Status, and Age when the creditor receives an application from a natural person and the credit is primarily for the purchase or refinance of a dwelling occupied or to be occupied by the applicant as their principal residence. The extension of credit will be secured by the dwelling.
If you are not subject to HMDA or Part 27, you must collect under Reg. B requirements or it will be a violation of ECOA.