Plaia v. Plaia, 450 P.3d 80

Alina and Michael Plaia married in 2001; Alina co-founded Wide Bridge and procured Luxoft as a client. Luxoft agreed to grant Alina up to 29,412 shares as compensation for her work; 5,886 were delivered and subject to vesting conditions.
The parties separated in 2014; both litigated divorce actions (Utah retained jurisdiction). In disclosures, Alina listed all 29,412 Luxoft shares as her asset (noting 5,886 vested).
In October 2014 the parties executed a mediated Stipulation dividing marital property: each was to receive one-half of 23,526 unvested Luxoft shares and one-half of the 5,886 vested shares; sale and accounting provisions accompanied the split.
Alina later sought to set aside the Stipulation, arguing mutual mistake (she and Michael believed she had already earned/vested the remaining shares) and that the division was inequitable because Michael did not contribute to post-separation vesting.
The district court held a bench trial, found no mutual mistake, credited that Alina knew vesting occurred over time and that she had declared ownership earlier, and concluded the stipulated division was not so inequitable as to warrant rescission. The court entered a divorce decree enforcing the Stipulation.
On appeal, the Utah Court of Appeals affirmed, concluding the district court did not abuse its discretion in enforcing the Stipulation or in its equitable property division.

Issue	Plaintiff's Argument (Alina)	Defendant's Argument (Michael)	Held
Whether the Stipulation should be rescinded for mutual mistake about the status of Luxoft shares	Alina: both parties believed the remaining shares were already earned/vested; mutual mistake warrants rescission	Michael: parties knew shares were vested/unvested and that vesting would occur over time; no mutual mistake of material fact	Court: No mutual mistake proved by clear and convincing evidence; Stipulation enforced
Whether the division of Luxoft shares in the Stipulation was inequitable	Alina: awarding Michael half of unvested shares is unfair because he did not contribute to vesting and he kept his 2014 distributions	Michael: parties negotiated and stipulated to the split; stipulations are entitled to great weight and are presumptively valid	Court: Division not so inequitable to set aside; district court did not abuse discretion

Baker v. Baker, 866 P.2d 540 (Utah Ct. App. 1993) (deferential review of trial court fact findings)
Pearson v. Pearson, 561 P.2d 1080 (Utah 1977) (trial court’s broad equitable power in property division and respect for stipulations)
Ashby v. Ashby, 227 P.3d 246 (Utah 2010) (spousal contracts enforceable under ordinary contract principles in divorce)
Deep Creek Ranch, LLC v. Utah State Armory Bd., 178 P.3d 886 (Utah 2008) (rescission for mutual mistake requires mistake as to a basic assumption of the contract)
Mabey v. Kay Peterson Constr. Co., 682 P.2d 287 (Utah 1984) (burden of proving mutual mistake by clear and convincing evidence)
Colman v. Colman, 743 P.2d 782 (Utah Ct. App. 1987) (appellate deference to trial court property divisions absent manifest injustice)