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# transactionId

The unique identifier for a transaction, such as an In-App Purchase, restored purchase, or subscription renewal.

```
string transactionId
```

## Discussion

The App Store generates a new value for transaction identifier every time the subscription automatically renews or the user restores it on a new device.

When a user first purchases a subscription, the transaction identifier always matches the original transaction identifier ([`originalTransactionId`](/documentation/AppStoreServerNotifications/originalTransactionId)). For a restore or renewal, the transaction identifier doesn’t match the original transaction identifier. If a user restores or renews the same subscription multiple times, each restore or renewal has a unique transaction identifier.

---

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