> ## Documentation Index
> Fetch the complete documentation index at: https://unevenlabs-docs-drift-src-aa153b3060-2d3471a.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Transaction Screening

> Understand address screening and blocked transactions on the Relay platform

The [Relay platform](/what-is-relay) screens transaction addresses using third-party risk data and an internal blocklist. Screening can prevent a quote or fill from proceeding.

## How It Works

Screening uses:

* **Third-party data** — Risk and sanctions databases, including HackBounty and Chainalysis, identify flagged addresses.
* **Internal blocklist** — The platform maintains additional address restrictions based on threat reports and investigations.

## Blocked Transactions

A flagged address can produce a “Detected sanctioned address” notification or a blocked-wallet error. See [Unsupported Exchanges](/security/unsupported-exchanges) before sending from an exchange.

A fill-time screening failure does not trigger an automatic refund. See [Execution Errors](/references/api/api_core_concepts/execution-errors) and contact [Support](/resources/support) for review.


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