InterestDue is a service operated by Harper AI, Inc., a Delaware corporation (“InterestDue,” “we,” “us”). By using this site you agree to these terms. InterestDue helps construction subcontractors calculate the statutory interest and prompt-payment amounts they may be owed on late payments, and generate demand letters from their own records.
What this service is – and is not
InterestDue is self-help software. Every figure it produces is a computation from the information you enter, applied under published statutes that are cited alongside the figure. The software presents the same statute-derived computations and the same neutral descriptions of options to every user; it does not give advice tailored to your situation.
InterestDue is not a law firm, is not a collection agency, and does not provide legal advice. This software is not a substitute for the advice of an attorney. For any dispute, or before relying on any deadline, consult a licensed attorney in your state.
Your letters, your name
Demand letters are generated from your records, on your letterhead, and sent by you. We never send letters in our own name, never contact the parties who owe you, never take assignment of or purchase any receivable, and never charge a percentage of what you recover. You are the sender of every letter, and you are responsible for its accuracy and for how you use it.
Your account
You sign in with a magic link sent to your email address. You are responsible for the security of that inbox and for activity under your account. Provide accurate information; we may suspend or terminate accounts that violate these terms, abuse the service, or create risk for us or other users.
Acceptable use
- No scraping, reverse-engineering, or bulk extraction of the site or its content.
- No unlawful use, harassment, or misrepresentation in any letter you send.
- Do not represent InterestDue or Harper AI, Inc. as the sender of a letter, as your agent, or as a collection agency – we are none of these.
- Enter only information you have the right to use, and keep it truthful – every output is computed from your inputs.
- No interfering with the service, probing for vulnerabilities, or circumventing rate limits.
You confirm every figure
Interest and penalty figures are computations from the contract dates, invoice amounts, and payment records you enter, under the cited statutes as of the dates shown. You confirm your inputs and review every letter before sending it. Deadline information (including lien and notice clocks) is informational only, can change, and must be verified with counsel before you rely on it – statutes are amended and courts interpret them.
Payments
InterestDue is a subscription shown at its current price before you buy, with a 14-day free trial. Payments are processed by Stripe; we do not store your card details. Subscriptions renew automatically until canceled – you can cancel any time from your account’s billing portal, effective at the end of the paid period. See our Refund Policy.
Disclaimer of warranties
The site and its outputs are provided “as is” and “as available,” without warranties of any kind, express or implied, including accuracy, completeness, merchantability, or fitness for a particular purpose. We do not warrant that any computed amount is collectible or that any letter will produce payment.
Limitation of liability
To the fullest extent permitted by law, InterestDue (Harper AI, Inc.) is not liable for any indirect, incidental, special, or consequential damages arising from your use of, or reliance on, the site or its outputs – including the outcome of any payment demand, any amount you do not recover, or any statutory deadline that passes. Our total liability for any claim is limited to the amount you paid us in the twelve months before the claim arose, or $100 if you paid nothing. Your sole additional remedy is to stop using the site.
Governing law & changes
These terms are governed by the laws of the State of California. We may update these terms; the effective date above marks the current version, and continued use after a change is acceptance.