Oregon late fee law

9%per year

Attaches to the debt by operation of law when you agreed no rate, so it accrues before any lawsuit and can be stated on a demand letter.

9% per annum when the parties have not otherwise agreed: applies to all moneys after they become due (open accounts bear interest from the date of the last item), money retained beyond a reasonable time, contracts to pay interest with no rate specified, and judgments. Full text verified at oregon.public.law (faithful republication of the official ORS; the official oregonlegislature.gov page was unreachable during research).

Parties may agree to a different rate. For loans of $50,000 or less, ORS 82.010(3) caps interest at the greater of 12% per annum or 5 percentage points above the Federal Reserve discount rate on 90-day commercial paper, subject to the exemptions in ORS 82.025 (e.g., financial institutions and licensed lenders). Commercial loans above $50,000 are effectively uncapped by this section. Verify exemption details with counsel.

public+private-construction

Public improvement contracts: ORS 279C.570 requires prompt payment (interest starts 30 days after invoice receipt or 15 days after payment approval, whichever is earlier) at a rate equal to three times the Federal Reserve 90-day commercial-paper discount rate, capped at 30% per annum. Private construction contracts have billing/payment provisions at ORS 701.620 et seq. (rate under those sections not independently verified - verify with counsel). No general private commercial (non-construction) prompt-payment statute found.

No Oregon statute specifically regulating flat late fees on B2B invoices was found; agreed late fees are generally enforceable if reasonable under liquidated-damages/penalty doctrine. Note ORS 82.010's open-account rule (interest from date of last item) is a distinctive default for trade accounts.