Applicant applies for individual, secured credit and completes the application as requested. Applicant list spouse's income and includes it with the total monthly income on the application. Spouse is not an applicant and will not be a signer on the loan.

Could this be an Reg. B violation?

No, and if the applicant wishes to rely on the spouse's income to qualify for the loan you can request verification of the income pull her credit report and require her to sign the necessary documents under state law to obligate her income to the loan.

We have a similar situation. An applicant listed her spouse's income as additional income and provided documentation of it. Her spouse would not be a signer on the loan. The applicant has a large amount of debt in her name. The lender was not comfortable with making the loan and turned it down based on her DTI. I'm wanting to make sure there would be no Reg B issue.

No there wouldn't be. If the spouse refuses to obligate the income for repayment of the debt you do not have to use it in your decision. Review the Commentary to 202.7(d)(5)(2).