I have 3 different scenarios and all three are reporting a different month. What is the correct way to count/disclose this?

Scenario 1 - Construction, 1 year loan term, 11 mo. interest only, fixed rate. Loan originated 8.7.23, first interest only payment due 9.15.23, balloon final payment 8.15.24 (374 days). System disclosed "Includes only interest and no principal until month 13"

Scenario 2 - Construction, 1 year loan term, 11 mo. interest only, fixed rate. Loan originated 7.27.23, first interest only payment due 8.27.23, balloon final payment 7.27.24 (366 days). System disclosed "Includes only interest and no principal until month 11"

Scenario 3 - Construction, 1 year loan term, 11 mo. interest only, fixed rate. Loan originated 6.2.23, first interest only payment due 7.2.23, balloon final payment 6.2.24 (366 days). System disclosed "Includes only interest and no principal until year 1"

Do we count from the due date of the initial periodic payment? Is the "until" month/year supposed to be the due date of the last interest only periodic payment?

Which scenario above is correct?

Thanks in advance for the help!

Scenario 1 - I am not sure how anyone can make such a loan as the loan term exceeds 12 months (374 days) and under the ATR rules, the balloon payment would have to be considered in the ability to repay.

Scenario 2 - that is correct.

Scenario 3 - Sounds like your LOS has a problem, as that transaction is no different than Scenario 2.

That brings me to a question about 30-year loans. If a loan closes on 8.4.2023, the first payment is 10.1.23, and the maturity date is 9.1.2053, then the time from origination to maturity is 360 months 28 days. However, the amortization period is 360. Is this why this loan is considered not to exceed 30 years and under the QM rules?

The 30-year rule is based on amortization and not closing to maturity. Otherwise, every 30-year secondary market loan would not qualify.

43(b)(6) Loan term.
1. General. The loan term is the period of time it takes to repay the loan amount in full. For example, a loan with an initial discounted rate that is fixed for the first two years, and that adjusts periodically for the next 28 years has a loan term of 30 years, which is the amortization period on which the periodic amortizing payments are based.

Thanks for the help!!!

Don't mean to beat a dead horse, but would 1026.17(c)(4) have any bearing on a construction loan or other temporary financing being able to go a few days past 365 days and still qualify for the ATR exemption?

No. 1026.17(c)(4) deals with the options for disclosing the payment schedule based on an odd day first period.
From the OI:

1. Payment schedule irregularities. When one or more payments in a transaction differ from the others because of a long or short first period, the variations may be ignored in disclosing the payment schedule pursuant to § 1026.18(g), the disclosures required pursuant to §§ 1026.18(s), 1026.37(c), or 1026.38(c), or the finance charge, annual percentage rate, and other terms. For example: