Weiss v. Weiss, 261 P.3d 1034

Rayna and Scott Weiss were married in 1993; premarital agreement provided separate-property treatment upon divorce.
In 2004 Rayna loaned Scott $280,000, funds used to acquire 40% ownership held in Scott’s name; no express written interest term at that time.
By December 3, 2007 Scott repaid the $280,000 in nine payments (plus $0.10), with payment updates showing principal reduction and no protest by Rayna.
A 2009 dissolution awarded the 40% ownership to Scott and treated the loan as interest-free; Rayna appealed.
In 2010 this Court held the loan accrued 10% interest under § 31-1-106(1), remanding to calculate interest; district court found $49,954.79 in interest and that principal was paid in full by 2007.
The district court’s calculation relied on applying each payment to principal, not to accrued interest, consistent with the repayment schedule and Rayna’s later challenge was limited to interest allocation and prejudgment interest

Issue	Plaintiff's Argument	Defendant's Argument	Held
Allocation of repayments (principal vs interest)	Rayna argues repayments should first cover accrued interest	Weiss contends repayments were applied to principal per the schedule	Repayments applied to principal; principal paid in full; interest due on remaining principal calculated thereafter
Whether the principal was paid in full	Rayna contends some principal remains	Weiss maintains principal fully paid as of Dec 3, 2007	Principal paid in full as of December 3, 2007
Method of interest calculation	Rayna seeks different allocation, possibly higher interest	District Court used simple interest on unpaid principal; law of the case governs	10% annual interest on unpaid principal; simple interest method upheld; prejudgment interest not awarded

In re Marriage of Weiss, 357 Mont. 320 (2010 MT 188) (ten percent interest rate on loan from date funds transferred until paid in full (law of the case))
Becker v. Becker, 255 Mont. 357 (1992) (law of the case and binding effect on remand decisions)
Zavarelli v. Might, 239 Mont. 120 (1989) (guidance on applying appellate decisions on remand)