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updatedAt: 2026-07-16T14:42:55.000Z
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Fetch the complete documentation index at: https://docs.truelayer.com/llms.txt. Use this file to discover all available pages before exploring further. Append .md to any documentation page URL to get its markdown version.
# Data API v1 overview
Access identity, accounts, transactions and balance data for all integrated banks with a single interface.
### Integrating for the first time?
If this is your first time integrating with a Data product, use [the Data API v3.](https://docs.truelayer.com/truelayer/docs/enable-your-users-to-connect-their-bank-account)
These docs are specifically about Data v1. While v1 and v3 both enable the same use cases, the integration processes for each version of the product are significantly different.
## Available data
The Data API allows you to access the following data for connected accounts available from a provider:
* Account: account holder name, account number, IBAN etc
* Credit card: card network, last four digits, name on card etc
* Transactions: description, amount, category, merchant name etc
* Balances: current, available etc
* Regular payments: standing orders and direct debits
Use `/api/providers` endpoint to determine which data is available for each provider. The response includes `scopes` which contains a list of information relating to the account.
## Supported countries
See our **Supported Providers** page in Console for more info on which countries and providers we support.
## Authentication flow
We offer a ready-made UX flow for you to easily let users connect their bank accounts to your application, or you can build your own fully custom flow on top of our API.
If you are regulated, you have 2 options for your auth flow:
* Use our ready-made, customisable user journey
* Build your own
###
Non-regulated and agents of TrueLayer customers must use TrueLayer’s flow, which is customisable to fit seamlessly into your application.
Both regulated and non-regulated merchants can also:
* Easily reconnect with lapsed account connections with our re-authentication process.
* Understand how far users make it through the authentication journey with our auth journey analytics (private beta).
## Data types
### General
All of the responses returned by TrueLayer APIs are in **JSON** format. The description of the data types encoded in a JSON response is below.
| Type | Description |
| ---------- | ---------------------------- |
| `string` | A UTF-8 string |
| `datetime` | An ISO8601 encoded date time |
| `boolean` | true or false |
| `number` | A float number |
#### ISO20022 Text Fields
The Data API constrains some fields to be limited to ISO 20022 text format. These fields are typically used for names and references in bank payment requests.
Valid characters for such a text field include:
```
a-z
A-Z
0-9
/ – ? : ( ) . , ‘ +
space
```
Any other characters will result in a validation error.
### API response structure
All responses are JSON encoded.
#### Success
| Field name | Type | Description |
| ---------- | ----- | ------------------- |
| `results` | array | An array of objects |
```json Success response
{
"results": [
{
"hello": "world"
}
]
}
```
#### Error
Most Data API v1 calls return the
| Field name | Type | Description |
| ------------------- | ------ | ------------------------------------------------------ |
| `error` | string | An error code for classification. eg: `internal_error` |
| `error_description` | string | When possible, extra details about the specific error |
| `error_details` | object | Additional key/value error details if available |
```json Error response
{
"error": "internal_error",
"error_description": "Well, this is embarrassing!",
"error_details": {
"detail_key": "detail value"
}
}
```
The only exception to this is the error response for the `/connections/extend` endpoint. Error responses for this endpoint contain the following fields:
| Field name | Type | Required? | Description |
| ---------- | ------ | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `type` | string | Yes | A URI identifying the class of error. It's a stable link to documentation describing this error type, so you can branch on it programmatically and click through for more detail. |
| `title` | string | Yes | A short, human-readable summary of the error type. It stays the same for a given type and isn't specific to this individual occurrence. |
| `status` | string | Yes | The HTTP status code, repeated in the body. 400 indicates the request was invalid — in this case, a validation failure. |
| `instance` | string | Yes | The endpoint where the error occurred (the request path that failed). |
| `trace_id` | string | Yes | A unique identifier for this specific request. Log it and quote it to TrueLayer support when raising a ticket, as it's how we locate your exact call. |
| `errors` | object | No | Field-level validation detail. An object mapping each offending request field to an array of human-readable messages explaining what's wrong. A field can have multiple messages, and multiple fields can appear. |
```json
{
"type": "https://docs.truelayer.com/#connection-api-errors",
"title": "One or more validation errors occurred.",
"status": 400,
"instance": "/connections/extend",
"trace_id": "3dc845a2-93a2-4e12-940a-0a8aec24d0bc",
"errors": {
"ClientId": [
"The ClientId field is required."
]
}
}
```