If I have a DTI calculation of 88.636 that was relied on in making the credit decision, should this be reported on the LAR as 88.63 or 88.64?

In the Section-by-Section Analysis of the final rule, the CFPB discusses the fact that they had originally proposed truncating any digits beyond the first two decimal places. They received comments, however, that most underwriting systems would round rather than truncate in calculating CLTV. Thus they removed that part of the proposal.

Consequently, in the instance you cite, I would report 88.64.

See the discussion on page 66221 here .