In addition to determining which month's "applicable Treasury yield" to use as the base for your spread calculation, you must compare with "the annual percentage rate (APR) for the loan, as calculated and disclosed under Sec. 226.6 or 226.18 of Regulation Z." Notice that this part of the HMDA reg does not say the "disclosed APR." If the disclosed APR is later found to be out of tolerance, you could have violations of both Regs. Z and C.
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...gone fishing.