{"uid":"cap_J0EWO-9Um7lkhnLEQyZBQ","slug":"paidpilot-late-fee-calculator-59e19970","name":"PaidPilot Late Fee Calculator","description":"PaidPilot Invoice API: Late fee on an overdue invoice. Flat fee, monthly % or annual %, simple or compounding, with grace days. Returns days late, fee, new total and a paste-ready invoice line. Optional US state for the legal note. Not legal advice; state caps are NOT looked up.","url":"https://api.paidpilot.io/v1/late-fee?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"as_of":{"type":"string","pattern":"^\\d{4}-\\d{2}-\\d{2}$","description":"Date paid, or the date to calculate to, YYYY-MM-DD (default: today, UTC)"},"state":{"type":"string","description":"US state (2-letter) for the legal note"},"amount":{"type":"number","maximum":1000000000,"description":"Unpaid invoice amount","exclusiveMinimum":0},"currency":{"type":"string","default":"USD","description":"ISO-4217, default USD"},"due_date":{"type":"string","pattern":"^\\d{4}-\\d{2}-\\d{2}$","description":"Invoice due date, YYYY-MM-DD"},"fee_type":{"enum":["flat","monthly_percent","annual_percent"],"type":"string","description":"flat = one fixed fee; monthly_percent e.g. 1.5; annual_percent e.g. 18"},"flat_fee":{"type":"number","maximum":1000000,"minimum":0,"description":"Flat fee; required for fee_type=flat, optional one-time add-on otherwise"},"grace_days":{"type":"integer","default":0,"maximum":365,"minimum":0,"description":"Days after the due date before any fee applies"},"compounding":{"type":"boolean","default":false,"description":"false = simple interest (default); true = compounds (monthly: per 30 days; annual: daily)"},"rate_percent":{"type":"number","maximum":100,"minimum":0,"description":"Rate for monthly_percent / annual_percent"}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.01","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.01/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.01","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.01","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_WThdw7jnR3-V9R8GtTmZV","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.01","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates late payment fees on overdue invoices using flat, monthly percentage, or annual percentage methods with optional compounding and grace days, returning the fee amount, days late, new invoice total, and a paste-ready invoice line item.","exampleAgentPrompt":"My client owes $3,500 on an invoice that was due on March 1st — can you calculate the late fee as of today using a 1.5% monthly rate with a 10-day grace period, no compounding, and add a legal note for California?","exampleUseCases":[{"title":"Freelancer monthly late fee invoice","prompt":"I have a client who hasn't paid their $2,200 invoice that was due on April 15th. It's now May 20th. Can you calculate the late fee at 1.5% per month with no grace days and no compounding, and give me the line I can paste onto the invoice?"},{"title":"Annual percentage compounding overdue bill","prompt":"Calculate the late charge on a $15,000 unpaid invoice due January 1st, 2025, using an 18% annual rate with daily compounding and a 5-day grace period — what's the total owed as of today?"},{"title":"Flat fee penalty with state legal note","prompt":"My $850 invoice was due on February 28th and the client still hasn't paid. I charge a flat $50 late fee with a 7-day grace period. Can you work out how late it is and what the new total is, and include a Texas legal note?"}],"resultDescription":"Returns the number of days the invoice is late, the calculated late fee amount, the updated invoice total (original amount plus fee), a ready-to-paste invoice line item string, and an optional US state-specific legal note. All monetary values are in the specified currency (default USD).","failureModes":["Missing required fields (amount, due_date, fee_type) returns a 400 validation error","rate_percent not provided when fee_type is monthly_percent or annual_percent causes an error","flat_fee not provided when fee_type is flat causes an error","as_of date earlier than due_date results in zero or negative days late","Invalid ISO-4217 currency code may cause an error","amount exceeding 1,000,000,000 or rate_percent exceeding 100 will fail validation","Invalid date format (not YYYY-MM-DD) returns a pattern validation error"],"whenToPreferThis":"Choose this endpoint when you need a fast, structured late fee computation with a paste-ready invoice line item and optional US state legal context. It handles flat fees, monthly percentage, and annual percentage with simple or compound interest — ideal for freelancers, small business invoicing agents, or AR automation pipelines that need a formatted output rather than just a raw number. Not a substitute for legal advice on state usury caps.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-12T12:39:36.662Z","isFirstParty":false,"canonicalSlug":"paidpilot-late-fee-calculator-59e19970"}