OpenChainGraph Suite · ART-215 · US Mortgage Compliance

Reg Z Appendix J APR Solver

Class C · Machine-checked proof (Dafny)

Actuarial APR computation per 12 CFR 1026 Appendix J. Bracketed bisection on the general actuarial equation, with the odd-days fraction priced at simple interest per (b)(6) and only full unit-periods compounded. A rate is reported only when a sign-change bracket was established. Input for TRID APR accuracy and QM spread tests.

Reg Z Appendix J TRID APR Disclosure Bracketed Bisection Odd Days Support
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Loan Parameters
Total advance disbursed at consummation.
Regular periodic payment (P&I).
Total scheduled payments (e.g. 360 for 30yr).
12 = monthly, 52 = weekly, 365 = daily.
Days from consummation to first unit period. 0 = regular.
Days in one payment period (30 for monthly).
APR Result
Loan Summary
Execution Hash (SHA-256)