# PaidPilot Late Fee Calculator

> PaidPilot Late Fee Calculator is a paid API for AI agents from api.paidpilot.io, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-12).

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.

## Facts

- Endpoint: POST https://api.paidpilot.io/v1/late-fee?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/paidpilot-late-fee-calculator-59e19970
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_J0EWO-9Um7lkhnLEQyZBQ

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability paidpilot-late-fee-calculator-59e19970 -d '<json body>'
```

Example prompt: 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?

## When to prefer this

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.

## Known failure modes

- 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

## How this service works

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.

## Output

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).

## Request schema (JSON Schema)

```json
{
 "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"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/paidpilot-late-fee-calculator-59e19970/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.paidpilot.io](https://www.zero.xyz/host/api.paidpilot.io/llms.txt)