You can file an EC Sales List (ESL) return through VAT Filer as long as you're authorised to act as the agent for this.

To appoint an agent, the client will need to follow these steps:

1. Register for the ESL service.
2. Log on to the HMRC Online Services.
3. Appoint the agent using the Agent Reference.

You can find out more about these steps to authorisation on the HMRC site.