South Dakota Late Fee Calculator
Work out interest on an overdue B2B invoice under South Dakota law. The legal default rate — what applies when the contract is silent — is 15%, and the statute is quoted verbatim below. All math runs locally in your browser.
Category F default rate when no written rate is fixed, from the day the balance is due/ascertained.
Late fee breakdown
- Interest owed
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- Daily rate
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- Total (invoice + interest)
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Still unpaid? Generate a formal demand letter — it computes the interest and cites South Dakota's statute (SDCL 54-3-5, 54-3-16, 54-3-1.1) for you.
What South Dakota law actually says
Unless there is an express contract in writing fixing a different rate or the interest rate clearly appears on the bill, statement, or invoice, interest is payable on all moneys at the Category F rate of interest as established in § 54-3-16 after they become due [...] Any interest rate appearing on a bill, statement, or invoice may not exceed eighteen percent.
Quoted verbatim from the linked official source — not our paraphrase. How we source and re-check every row is documented in the data methodology.
Maximum late fee in South Dakota — written B2B contracts
Conditional cap 18% if the rate only appears on the bill, statement, or invoice; no cap if fixed by written agreement.
A rate fixed by written agreement — a document in physical or electronic form in which the parties have demonstrated their agreement to the rate — has no statutory maximum under SDCL 54-3-1.1. But that section applies only 'unless a maximum interest rate or charge is specifically established elsewhere in the code,' and SDCL 54-3-5 establishes one: a rate that merely appears on a bill, statement, or invoice may not exceed eighteen percent. Unilaterally printing 1.5%/month on an invoice is therefore the capped path, not the uncapped one.
Basis: SDCL 54-3-1.1; 54-3-5. Compare all 51 jurisdictions on the full state table and the cap-regime map.
B2B invoices only — not rent, not consumer debt
Everything on this page is about business-to-business invoices. Residential rent late fees live in South Dakota's landlord-tenant law and consumer credit has separate, stricter rules — two different bodies of law. The distinction is explained in B2B invoice late fees vs. residential rent.
Use this data
South Dakota's row — rate, cap, citation, verbatim quote, verification date — is part of our open 51-jurisdiction dataset: CSV · JSON (CC BY 4.0, cite myinvoicetemplate.com). Set late-fee terms on your next invoice with the free invoice generator, or state them clearly using the wording guidance in the payment terms guide.
South Dakota late fee FAQ
Can I charge late fees on overdue invoices in South Dakota?
Yes — on business-to-business invoices. If your contract or invoice states a late-fee rate, that rate governs (subject to the cap rules below). If nothing was agreed: 15%. Category F default rate when no written rate is fixed, from the day the balance is due/ascertained. Statute: SDCL 54-3-5, 54-3-16, 54-3-1.1, verified 2026-08-21. Consumer and rent debts follow separate laws.
What is the maximum late fee I can charge in South Dakota?
For a written B2B contract: No cap on a rate fixed by written agreement (SDCL 54-3-1.1) — unless a maximum is set elsewhere in the code, and one is: a rate that only appears on a bill, statement, or invoice may not exceed 18%. Basis: SDCL 54-3-1.1; 54-3-5. The full cap analysis is in the section above; this covers business-to-business deals only — consumer credit has stricter separate caps.
What interest applies if my contract doesn't mention late fees in South Dakota?
The statutory default rate of 15%. Category F default rate when no written rate is fixed, from the day the balance is due/ascertained. Statute: SDCL 54-3-5, 54-3-16, 54-3-1.1 (verbatim quote on this page, verified 2026-08-21).
Does this cover rent, apartment, or consumer late fees in South Dakota?
No. This page covers business-to-business invoices only. Residential rent late fees are governed by South Dakota's landlord-tenant law, and consumer credit for personal, family, or household purposes has its own stricter caps and disclosure rules. Those are different statutes than the commercial-interest law cited here.
Where does this data come from, and when was it verified?
Every figure on this page comes from our 51-jurisdiction dataset: each row researched against the controlling statute or the state's official current-rate page, independently re-checked, and stamped with its own verification date — South Dakota's row was last verified 2026-08-21. The operative legal text is quoted verbatim on this page with a link to the official source, the methodology is public, every verification pass is logged in the changelog, and the full dataset is downloadable (CC BY 4.0).
Not legal advice. This page summarizes South Dakota's commercial-interest statute for general information, with the verification date shown above — it tells you when we last confirmed the figures, not that they are still current today. Statutes change and courts interpret them; verify the cited statute at the official source, or ask a licensed attorney in your state, before charging or demanding interest.