Where an arbitral award is challenged for error in determining when statutory interest begins to accrue and in recognising monetary revaluation, the determination of the nature of the creditor's claim (whether arising from contractual breach or from restitution of undue payment) governs the applicable legal regime, with the consequence that interest runs from the date of breach rather than from the date of the claim where the obligation is synallagmatic.
Recognition of additional damages under Article 1224, paragraph 2, of the Civil Code in proceedings to set aside an arbitral award is admissible on a presumptive basis to the extent of the differential between the average annual net yield of government securities with a maturity not exceeding twelve months and the statutory interest rate, provided that the creditor makes specific application therefor and the economic parameter exceeds the statutory rate during the period of default.
A claim for additional damages from monetary devaluation in excess of the differential between government securities yield and statutory interest requires actual proof of damage suffered through adequate and complete documentation, it not being sufficient to rely on a generic expert report prepared by a party for other purposes and based on incomplete information.