Idaho Prejudgment Interest Rate
United States Idaho’s prejudgment interest rate — when a court awards it.
Set by statute Fixed by statute
Idaho prejudgment interest is 12% per year, as simple interest under Idaho Code 28-22-104(1). Prejudgment interest is available ONLY where the claim is liquidated OR the amount is ascertainable by a mere mathematical process.
When Idaho prejudgment interest applies
Prejudgment interest is available ONLY where the claim is liquidated OR the amount is ascertainable by a mere mathematical process. It is BARRED on unliquidated damages. Generally NOT available in tort cases unless the damages are reasonably ascertainable/liquidated (Davis v. Prof'l Bus. Servs.; Bouten Constr. v. H.F. Magnuson). Contract claims qualify when the sum due is fixed or mathematically determinable. If an express written contract sets a different interest rate, that rate applies instead of 12%.
When it starts accruing
Interest accrues from the date the money became "due" (for contract, the date of breach), provided that at that point the amount was liquidated or ascertainable by mathematical computation.
Simple or compound
Simple.
→ Compare with the Idaho post-judgment interest rate (interest after judgment)
Prejudgment interest under Idaho Code 28-22-104(1) — 12% (simple interest). This is PREjudgment interest (accruing before entry of judgment) and is separate from Idaho’s post-judgment rate; availability is limited by claim type (see the page). Verify against the statute text. Not legal advice.
Effective-date history
| Effective date | Rate | Basis |
|---|---|---|
| July 9, 2026 | 12% | Statute |
Source & provenance
Latest value retrieved July 10, 2026 (02:55 UTC) from the official source:
https://legislature.idaho.gov/statutesrules/idstat/title28/t28ch22/sect28-22-104/