Authentication

Overview

The Fifteenth Partner API uses Bearer token authentication with API keys. All requests must include a valid API key in the Authorization header to access protected endpoints.

Getting Started

Contact Partner Success

Email partners@fifteenth.com to request API access. Include:

Your company name and website
Estimated client volume
Integration timeline

Complete Onboarding

Our partner success team will guide you through:

Partnership agreement execution
Technical requirements review

Receive API Keys

Once onboarded, you’ll receive:

Production API key for live integration

API Key Authentication

Using Your API Key

Include your API key in the Authorization header of all requests:

Authorization: Bearer your_api_key_here

API Key Format

Fifteenth API keys follow this format:

15th_<random_string>

Example:
15th_M4pQ7vN9xR2mK5wL8S1E6B

Production Environment

Production

Purpose: Live client operationsEnvironment: Production with real client dataRate Limits: 100 requests/minute, 10,000/day

Request Examples

import requests

headers = {
    "Authorization": "Bearer 15th_your_api_key_here",
    "Content-Type": "application/json"
}

response = requests.get(
    "https://api.fifteenth.com/v1beta/accounts",
    headers=headers
)

if response.status_code == 200:
    accounts = response.json()
    print(f"Found {len(accounts)} accounts")
else:
    print(f"Error: {response.status_code}")

const headers = {
    'Authorization': 'Bearer 15th_your_api_key_here',
    'Content-Type': 'application/json'
};

const response = await fetch('https://api.fifteenth.com/v1beta/accounts', {
    method: 'GET',
    headers: headers
});

if (response.ok) {
    const accounts = await response.json();
    console.log(`Found ${accounts.length} accounts`);
} else {
    console.log(`Error: ${response.status}`);
}

curl -X GET "https://api.fifteenth.com/v1beta/accounts" \
  -H "Authorization: Bearer 15th_your_api_key_here" \
  -H "Content-Type: application/json"

Rate Limits

The API enforces rate limits to ensure fair usage:

Production: 100 requests per minute, 10,000 per day

When you exceed rate limits, the API returns a 429 Too Many Requests response:

{
  "error": {
    "code": "RATE_LIMIT_EXCEEDED",
    "message": "Rate limit exceeded. Please retry after 60 seconds.",
    "details": {
      "limit": 100,
      "window_seconds": 60,
      "reset_at": "2024-01-15T10:31:00Z"
    }
  }
}

Security Best Practices

API Key Security

Store Securely: Never commit API keys to version control
Use Environment Variables: Store keys in environment variables or secure configuration
Monitor Usage: Watch for unusual activity in your API usage

Implementation Example

import os
import requests

# Good: Use environment variables
api_key = os.environ.get('FIFTEENTH_API_KEY')
if not api_key:
    raise ValueError("FIFTEENTH_API_KEY environment variable not set")

headers = {"Authorization": f"Bearer {api_key}"}

Error Handling

Authentication Errors

Status Code	Error Code	Description	Solution
`401`	`INVALID_API_KEY`	API key is invalid or malformed	Check your API key format
`401`	`EXPIRED_API_KEY`	API key has expired	Contact support for a new key
`403`	`INSUFFICIENT_PERMISSIONS`	Key lacks required permissions	Verify your integration scope
`429`	`RATE_LIMIT_EXCEEDED`	Too many requests	Wait and retry with backoff

Example Error Response

{
  "error": {
    "code": "INVALID_API_KEY",
    "message": "The provided API key is invalid",
    "details": {
      "hint": "Ensure your API key starts with '15th_'"
    }
  }
}

Next Steps

Quickstart Guide

Make your first API call and create a client account

Create Account

Start by creating your first client account

Upload Documents

Learn how to upload tax documents

API Reference

Explore all available endpoints

Get Started

Health

Accounts

Documents

Projects

Deliverables

Overview

Getting Started

API Key Authentication

Using Your API Key

API Key Format

Production Environment

Production

Request Examples

Rate Limits

Security Best Practices

API Key Security

Implementation Example

Error Handling

Authentication Errors

Example Error Response

Next Steps

Quickstart Guide

Create Account

Upload Documents

API Reference

​Overview

​Getting Started

​API Key Authentication

​Using Your API Key

​API Key Format

​Production Environment

Production

​Request Examples

​Rate Limits

​Security Best Practices

​API Key Security

​Implementation Example

​Error Handling

​Authentication Errors

​Example Error Response

​Next Steps

Quickstart Guide

Create Account

Upload Documents

API Reference

Overview

Getting Started

API Key Authentication

Using Your API Key

API Key Format

Production Environment

Request Examples

Rate Limits

Security Best Practices

API Key Security

Implementation Example

Error Handling

Authentication Errors

Example Error Response

Next Steps