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

# How receipt providers work with OpenCard

> How receipt providers fit into OpenCard — collect receipts from merchants, handle match requests, deliver receipt callbacks, and enrich EMS transaction data.

You operate a **receipt collection network**. OpenCard connects your receipts to card transactions and passes enriched data to EMS integrators.

***

## Where you sit

```mermaid theme={null}
flowchart LR
    Merchants[Merchants / POS / E-com] -->|receipts| You[Receipt Provider]
    OC[OpenCard] -->|match request| You
    You -->|receipt callback| OC
    OC -->|webhooks| EMS[EMS apps]
```

1. You continuously **collect receipts** from merchants in your network
2. OpenCard receives a card transaction marked `receiptable: true`
3. OpenCard sends you the transaction details to match against your receipts
4. When you find a match, you **POST the receipt** to OpenCard
5. OpenCard stores the receipt, extracts VAT + line items
6. EMS apps receive `receipt.fetched`, `transaction.true.vat`, and `transaction.line.items` webhooks

You only integrate with OpenCard — not with EMS apps or card programs.

***

## What you deliver to OpenCard

| You send                       | OpenCard does              | EMS receives             |
| ------------------------------ | -------------------------- | ------------------------ |
| Receipt file (PDF, image, XML) | Stores file, generates URL | `receipt.fetched`        |
| VAT breakdown in receipt       | Creates TrueVAT records    | `transaction.true.vat`   |
| Line items in receipt          | Creates LineItem records   | `transaction.line.items` |

***

## Onboarding checklist

* [ ] Receive **client secret** from OpenCard
* [ ] Endpoint ready to **receive match requests** from OpenCard
* [ ] Implement **outbound callback** to OpenCard (`POST /v1/service/marcet/callback/{referenceId}`)
* [ ] Handle `CallbackRequestResolved` and `CallbackRequestDeleted`
* [ ] Sign every payload with HMAC-SHA256

→ [Callback delivery](/receipt-providers/callback-delivery) for endpoint details.

Contact **[support@opencard.io](mailto:support@opencard.io)** to get started.