We have a mortgage loan that will not qualify under the general qualified mortgage rule so we are qualifying it under a small creditor so as not to worry about the 43% DTI. This is where my question comes into play. The customer's back end DTI ratio is very high. If we have verified the 8 factors for the ATR are we ok to make the loan?

This would/should be addressed in your loan policy i would think. While small creditors don't have to adhere to a hard and fast 43% DTI ratio, that doesn't mean they can disregard DTI. It's really as much of a S&S concern as it is a compliance one: how comfortable would your bank be that someone with a (you didn't say how high, so i'm just throwing numbers out there) 65% or 70% DTI could repay the loan? If the answer is "not very", then you'd have double incentive to not make the loan. If by very high you just mean 48% or something that falls below your internal policy, then you'd probably be ok. Just my thoughts.

I agree with raitchjay. Document what factors exist that make you comfortable with making the loan. For example, "applicant has had a mortgage with us for 8 years and never made a payment late"; or, "applicant is refinancing and reducing his monthly payment by $250."