# Platform APIs

The Digital Post Platform exposes a set of REST APIs that enable secure digital message delivery and operational monitoring.

Each API has a clearly defined responsibility. You can integrate a single API for a focused use case or combine both to build a complete delivery flow.

All APIs require authenticated access using machine identities.

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Delivery API
Submit deliveries using S3 based integration or multipart form data upload. Each delivery contains one or more envelopes with recipients, content, and allowed message actions.

Billing API
Access billing and usage data for your organisation's message deliveries.

## How the APIs work together

The **Delivery API** is the core of every sender integration — use it to submit messages to recipients on the platform.

The **Billing API** provides visibility into delivery volumes and costs, supporting internal reporting and reconciliation.

## Before you start

Ensure that:

- A system integration has been created
- A client certificate is registered
- Required sender identities exist
- Appropriate permissions are assigned


See [Authentication](/api/authentication) for token generation.