Get expense data from FreshBooks API

Introduction

This article is part of an in-depth series on the FreshBooks API, designed for teams building reliable accounting integrations at scale. In this piece, we focus on a high-frequency use case: retrieving expense data from FreshBooks.

Expense data is foundational for downstream workflows, financial reporting, reimbursements, budgeting, and analytics. While FreshBooks provides a clean API, teams often underestimate the operational complexity around authentication, pagination, rate limits, and long-term maintenance.

If you’re looking for a broader overview of FreshBooks API authentication, limits, and core objects, refer to the complete FreshBooks API guide here.

Prerequisites

Before you start, make sure the basics are in place:

• A FreshBooks developer account with API access
• OAuth 2.0 authentication fully configured
• A Python environment with the requests library installed

If OAuth isn’t already set up, stop here and do that first. Nothing else works reliably without it.

API Endpoint

FreshBooks exposes expenses through the Accounting API:

GET https://api.freshbooks.com/accounting/account/{accountid}/expenses/expenses


You’ll need the correct accountid, which is often a source of confusion for first-time integrators.

Step-by-Step Process

1. Authenticate with OAuth 2.0

All FreshBooks API calls require a valid OAuth 2.0 access token. This token must be passed in the Authorization header as a Bearer token.

Key point: access tokens expire. Your integration must support token refresh from day one.

2. Fetch Expense Data

Below is a simple Python example to retrieve expense data for a given account.

import requests

def get_expenses(account_id, access_token):
    url = f"https://api.freshbooks.com/accounting/account/{account_id}/expenses/expenses"
    headers = {
        "Authorization": f"Bearer {access_token}",
        "Content-Type": "application/json"
    }

    response = requests.get(url, headers=headers)

    if response.status_code == 200:
        return response.json()
    else:
        raise Exception(
            f"Error fetching expenses: {response.status_code} - {response.text}"
        )

# Example usage
account_id = "your_account_id"
access_token = "your_access_token"

expenses = get_expenses(account_id, access_token)
print(expenses)

In production, this function should also handle pagination, retries, and token refresh logic. The example above is intentionally minimal.

Common Pitfalls (Read This Before Shipping)

This is where most integrations fail, not at the API call, but in the operational gaps around it.

1. Expired or invalid access tokens
   Token refresh isn’t optional. If you hard-code tokens, your integration will break.
2. Incorrect account ID
   FreshBooks users can have multiple accounts. Pull and store the correct one explicitly.
3. Ignoring pagination
   Expense lists grow quickly. Always assume responses are paginated.
4. Rate-limit blind spots
   Burst traffic or background sync jobs can silently hit limits and drop data.
5. Wrong API version assumptions
   FreshBooks evolves its APIs. Don’t assume backward compatibility.
6. Weak error handling
   Treat non-200 responses as first-class states, not edge cases.
7. No retry or backoff strategy
   Network failures happen. Your integration should recover without manual intervention.

Bottom line: most FreshBooks “API issues” are actually integration design issues.

Frequently Asked Questions

How do I get an access token?
You must authenticate using OAuth 2.0 and complete the authorization flow to obtain an access token.

What happens when the access token expires?
Use the refresh token issued during authentication to generate a new access token automatically.

Can I filter expenses by date or other attributes?
Yes. FreshBooks supports query parameters for filtering. Refer to the official documentation for supported fields.

What are the API rate limits?
Rate limits vary by endpoint and usage pattern. Always design defensively and consult FreshBooks’ latest API docs.

How should API errors be handled?
Log them, categorize them (auth, rate limit, server), and retry only when appropriate. Silent failures are unacceptable.

Is there a limit to how many expenses I can fetch?
Large datasets are paginated. Your integration must iterate through pages until completion.

Can the same approach be used for other FreshBooks data?
Yes. Invoices, clients, payments, and other objects follow similar authentication and request patterns.

Using Knit for FreshBooks API Integration

If you don’t want to spend engineering cycles on OAuth flows, token refresh, pagination, retries, and long-term API maintenance, this is where abstraction makes sense.

Knit provides a unified API layer for FreshBooks. You integrate once, and Knit handles:

• Authentication and token lifecycle management
• API version changes and edge cases
• Ongoing maintenance as FreshBooks evolves

For teams scaling accounting integrations across customers and geographies, this approach materially reduces risk, build time, and maintenance overhead.

‍