DueDateCaps
Some contracts or laws cap late charges, for example at a percentage of the invoice. The API applies a cap by percent or amount (the lower wins), keeping the flat fee first and reducing interest.
API
On Starter, Team and Business plans, POST /v1/late-fee returns days late, a flat fee, interest and total due with a step-by-step explanation. It also supports monthly rates (simple or compounded), caps, business-day grace periods using DueDate holiday calendars, and due dates computed from an invoice date and term like Net 30. Each request counts as one API call. See pricing.
FAQ
Can I cap the late charges?
Yes, in the API: capPercent (of the invoice) or capAmount. If both are set, the lower cap applies.
Can it compute the due date from Net 30?
Yes, in the API: pass invoiceDate and term (for example net30) instead of dueDate, with optional holiday calendar.
Is this legal advice?
No. DueDate only does the arithmetic. Check your contract and your state's law before charging late fees or interest; many states cap them.
How is rounding done?
Interest and percentage-based fees are each rounded to the nearest cent, half away from zero.