Teller API: Real-Time Banking Data for Fintech Solutions

Teller API — Open Banking for US Bank Accounts

If you're building a fintech app that needs real, live bank data from US financial institutions, the Teller API is one of the most developer-friendly and direct-connection solutions available today. Unlike screen-scraping methods or credential-based aggregation, Teller connects directly to US banks, giving your application accurate, real-time account and transaction data — without the reliability headaches.

At FintegrationFS, we've integrated Teller API into production fintech products for US-based startups, credit platforms, and personal finance tools. Here's everything you need to know — from what it does to how to implement it.

What Is the Teller API?

The Teller API is an open banking platform built specifically for the United States market. It provides direct, bank-certified connections to hundreds of US financial institutions, allowing developers to access account balances, transaction history, and payment initiation through a clean, modern REST API.

Where most open banking APIs rely on credential-based scraping or third-party data brokers, Teller takes a different approach — it uses direct bank integrations and certificate-based authentication, which means the data is more reliable, more real-time, and more secure.

It's a strong fit for US fintech teams building: personal finance apps, lending underwriting tools, payroll verification platforms, B2B expense management tools, and account-to-account payment flows.

Core Capabilities of Teller API

Account Information — Access real-time balances, account types, routing numbers, and institution details from connected bank accounts.

Transactions — Retrieve enriched, categorized transaction history with merchant names, amounts, and dates. Ideal for budgeting tools and underwriting.

Identity — Pull account holder name and contact details to support KYC flows and identity matching.

Payment Initiation — Initiate bank-to-bank transfers directly through connected accounts (availability depends on institution).

Webhooks — Receive event-driven notifications for new transactions, balance changes, and account updates without constant polling.

Sandbox Environment — A fully featured test environment with simulated bank accounts, so your team can build and QA without touching real data.

Teller API vs. Alternatives — Feature Comparison

How Teller API Works

Teller uses mutual TLS (mTLS) and OAuth2 for secure bank connections. When a user links their bank account, Teller handles the authentication handshake directly with the financial institution — your app never sees or stores raw banking credentials.

The typical integration flow looks like this:

1. User opens your app and initiates bank account linking

2. Teller Connect (SDK) launches an in-app authentication modal

3. The user selects their bank and authenticates

4. Teller exchanges a secure token with the bank

5. Your backend receives an enrollment_id and access_token

6. You use the access token to query the Teller REST API for account data

Fetching Account Balances with Teller API 

const axios = require('axios');

// Teller API base URL
const TELLER_BASE_URL = 'https://api.teller.io';

// Access token received after user enrollment
const ACCESS_TOKEN = 'your_teller_access_token';

// Certificate-based auth (Teller requires mTLS)
const fs = require('fs');
const https = require('https');

const tlsAgent = new https.Agent({
  cert: fs.readFileSync('./teller_cert.pem'),
  key: fs.readFileSync('./teller_key.pem'),
});

async function getAccounts() {
  try {
    const response = await axios.get(`${TELLER_BASE_URL}/accounts`, {
      httpsAgent: tlsAgent,
      auth: {
        username: ACCESS_TOKEN,
        password: '',  // Teller uses token as username, empty password
      },
    });

    const accounts = response.data;
    accounts.forEach(account => {
      console.log(`Account: ${account.name}`);
      console.log(`Type: ${account.type}`);
      console.log(`Balance: $${account.balance.available}`);
      console.log(`Institution: ${account.institution.name}`);
      console.log('---');
    });
  } catch (error) {
    console.error('Teller API Error:', error.response?.data || error.message);
  }
}

getAccounts();

Code Example — Fetching Transactions (Node.js)

async function getTransactions(accountId) {
  try {
    const response = await axios.get(
      `${TELLER_BASE_URL}/accounts/${accountId}/transactions`,
      {
        httpsAgent: tlsAgent,
        auth: {
          username: ACCESS_TOKEN,
          password: '',
        },
      }
    );

    const transactions = response.data;
    transactions.forEach(txn => {
      console.log(`Date: ${txn.date}`);
      console.log(`Description: ${txn.description}`);
      console.log(`Amount: $${txn.amount}`);
      console.log(`Category: ${txn.details.category}`);
      console.log('---');
    });
  } catch (error) {
    console.error('Transaction fetch error:', error.response?.data || error.message);
  }
}

Teller API Response Structure — Account Object

{
  "id": "acc_o2taan3mg2dk7in3ak000",
  "enrollment_id": "enr_o2taan3mg2dk7in3ai000",
  "institution": {
    "name": "Chase",
    "id": "chase"
  },
  "name": "Premier Checking",
  "currency": "USD",
  "last_four": "4567",
  "links": {
    "balances": "https://api.teller.io/accounts/acc_o2taan3mg2dk7in3ak000/balances",
    "self": "https://api.teller.io/accounts/acc_o2taan3mg2dk7in3ak000",
    "transactions": "https://api.teller.io/accounts/acc_o2taan3mg2dk7in3ak000/transactions"
  },
  "status": "open",
  "subtype": "checking",
  "type": "depository"
}

Common Use Cases for Teller API in US Fintech Apps

Personal Finance & Budgeting — Aggregate all of a user's bank accounts in one view. Show spending trends, categorized transactions, and savings insights automatically.

Lending & Credit Underwriting — Pull 90-day transaction history to assess cash flow, income consistency, and repayment capacity — replacing manual bank statement uploads.

Payroll & Income Verification — Verify direct deposits and recurring income streams in real time, reducing fraud in loan applications and rental approvals.

Account-to-Account Payments — Initiate bank transfers without card rails, reducing payment processing fees for B2B and peer-to-peer platforms.

Expense Management — Automatically categorize and sync business account transactions into accounting tools or internal dashboards.

How FintegrationFS Integrates Teller API

We don't just hand you documentation links. Our team handles the full Teller API integration lifecycle for your US fintech product:

• mTLS certificate setup and secure credential management

• Teller Connect SDK implementation (iOS, Android, React Native, Web)

• Backend API layer for token management, webhooks, and data sync

• Database schema design for storing enriched transaction data

• Error handling, retry logic, and enrollment refresh flows

• Testing in Teller's sandbox before production go-live

We've shipped production integrations for lending platforms, neobanks, and personal finance apps — and we know exactly where Teller integrations tend to break under edge cases.

FAQ

What is the Teller API used for? 

The Teller API is used to connect US bank accounts to fintech applications. It gives developers access to real-time account balances, transaction history, identity data, and payment initiation — all through a secure REST API with direct bank connections.

How is Teller API different from Plaid? 

The main difference is in how they connect to banks. Teller uses direct bank integrations with mTLS authentication, which tends to produce more reliable and real-time data. Plaid has broader institution coverage (12,000+) but uses a mix of direct and credential-based connections. For US-focused apps prioritizing data accuracy, Teller is a strong alternative worth evaluating.

Is Teller API available outside the United States? 

Currently, Teller API is built specifically for the US banking market. It supports connections to major US financial institutions including Chase, Bank of America, Wells Fargo, Citi, and hundreds more.

Does Teller API store user banking credentials? 

No. Teller never stores your users' banking usernames or passwords. It uses certificate-based authentication and OAuth flows to securely connect directly with financial institutions.

What US banks does Teller API support? 

Teller supports 5,000+ US financial institutions including major banks (Chase, Bank of America, Wells Fargo, US Bank, Citi), credit unions, and regional banks. Coverage continues to expand.

How long does it take to integrate Teller API into an app? 

A basic integration — account linking, balance fetch, and transaction pull — can be completed in 1 to 2 weeks by an experienced developer. A production-grade integration with webhook handling, error recovery, and a polished UI typically takes 3 to 5 weeks.

Is Teller API compliant with US financial regulations? 

Teller is designed with US compliance requirements in mind, including data security standards aligned with financial industry expectations. Your legal and compliance team should review specific regulatory obligations (GLBA, CCPA, etc.) for your product.

Can FintegrationFS help us integrate the Teller API? 

Yes. FintegrationFS specializes in Teller API integration for US fintech products. We handle everything from certificate setup and SDK implementation to backend infrastructure and go-live testing. Contact us to discuss your project.