> ## Documentation Index
> Fetch the complete documentation index at: https://developers.pleo.io/llms.txt
> Use this file to discover all available pages before exploring further.

# AS/ERP (Accounting) Integration Overview

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This page provides a **high-level overview** of custom Accounting Integrations between Pleo and external Accounting Systems (AS) or Enterprise Resource Planning (ERP) systems.

It explains **what accounting integrations are**, **which integration levels are available**, and **where to go next** depending on your implementation needs.

## What Is an Accounting Integration?

An Accounting Integration allows an ERP or Accounting System to **receive accounting-ready data from Pleo** using Pleo APIs.

These integrations are typically used when:

* No pre-built integration exists
* Custom bookkeeping logic is required
* Advanced automation or synchronisation is needed
* The ERP system requires a bespoke deployment model

Accounting Integrations are **export-driven** and focus on moving expenses, attachments, and related accounting data from Pleo into an external system in a predictable and auditable way.

<NoteCallout title="Pre-built Integrations">
  If your system is supported out of the box, you may prefer a [pre-built integration](/docs/current/how-tos/how-to-connect-pleo-to-pre-built-as-systems).
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## Integration Levels

Accounting Integrations can be implemented at different **levels**, depending on which APIs are used and how much automation is required.

| Level   | Export | Tags | Categories | Vendors | Corresponding APIs                                                |
| :------ | :----- | :--- | :--------- | :------ | :---------------------------------------------------------------- |
| Level 1 | ✅      |      |            |         | Export API                                                        |
| Level 2 | ✅      | ✅    |            |         | Export API + Tags API                                             |
| Level 3 | ✅      | ✅    | ✅          |         | Export API + Tags API + Accounts API + Tax Code API               |
| Level 4 | ✅      | ✅    | ✅          | ✅       | Export API + Tags API + Accounts API + Tax Code API + Vendors API |

**How to choose a level:**

* **Level 1**\
  Enables exporting expenses and attachments. Suitable for basic accounting workflows.

* **Level 2 (recommended minimum)**\
  Adds Tags Sync, which syncs Accounting Dimensions from the Accounting System into Pleo as Tags. Users assign tags when they submit an expense; bookkeepers can assign or update them further before export.

* **Level 3**\
  Adds Chart of Accounts Sync and Tax Code Sync. Chart of Accounts are synced from the Accounting System into Pleo and mapped to expense categories; users assign a category when they submit an expense and bookkeepers can assign or update it before export. Accounts can optionally carry a `taxCodeExternalId` as a reference to a tax code in the Accounting System. Tax codes are synced separately via the Tax Code API.

* **Level 4**\
  Adds Vendor Sync, which is bi-directional. Vendors are synced from the Accounting System into Pleo. The integration can also listen for new vendors via the `v1.vendor.created` webhook and update the Accounting System with the details.

## Deployment Overview

Accounting Integrations can be deployed in different ways depending on the target ERP or Accounting System.

At a high level, integrations are deployed either:

* **As a module / on-premises**, hosted inside the ERP environment
* **On a cloud platform**, hosted externally and connected through OAuth 2.0

Each [deployment model](/docs/current/getting-started/accounting-integrations-deployment-decisions) affects how users authenticate, where configuration lives, and how authorisation is handled.

## Authentication & Authorisation

All Accounting Integrations use **OAuth 2.0** to securely access Pleo APIs.

* Users authorise access from within Pleo
* Tokens are issued and managed by the integration
* Scopes determine which APIs and data can be accessed

Authentication behaviour varies slightly depending on deployment model, but **OAuth 2.0 remains the single authorisation mechanism**.

***

## What Comes Next?

Start by getting access to the staging environment and setting up authentication, then build up through the integration levels in order.

**1. Get access**

* [OAuth 2.0 Access to Staging](/docs/current/guides/environment-access/staging-oauth-workflow)
* [OAuth 2.0 Setup Workflow Guide](/docs/current/guides/oauth-workflow-guide)

**2. Level 1: Export Integration**

* [Integration Design: Export Overview](/docs/current/integration-design/exports/integration-design-exports-overview)
* [Export Integration Workflow Guide](/docs/current/guides/export-integration-workflow-guide)

**3. Level 2: Tags Sync**

* [Integration Design: Tags Sync Overview](/docs/current/integration-design/accounting-integrations/imports/tags/integration-design-tags-overview)
* [Tags Sync Workflow Guide](/docs/current/guides/accounting-integrations/imports/tags-sync-workflow-guide)

**4. Level 3: Chart of Accounts and Tax Code Sync**

* [Integration Design: Chart of Accounts Sync Overview](/docs/current/integration-design/accounting-integrations/imports/accounts/integration-design-accounts-overview)
* [Chart of Accounts Sync Workflow Guide](/docs/current/guides/accounting-integrations/imports/accounts-sync-workflow-guide)
* [Tax Codes API Reference](/reference/tax-codes-overview)

**5. Level 4: Vendor Sync**

* [Vendors API Reference](/reference/vendor/vendors-api-overview)

***

## Related Reading

* [Accounting Integration Deployment Decisions](/docs/current/getting-started/accounting-integrations-deployment-decisions)
* [AS/ERP Processing Workflow Guide](/docs/current/guides/accounting-system-processing-workflow-guide)

***