Surveillance and main audits

Answer: A surveillance audit is an audit performed by the certification body between the certification and recertification audits, to check if the system is maintained.

2 - How is it different from the main audit?

Answer: While a main audit (for certification or recertification) covers all the certification scope, a surveillance audit covers only part of the certification scope. After a certification, the surveillance audits are planned in such a way that all the certification scope is audited before the recertification audit is performed.

This article will provide you further explanation about audits:
- Surveillance visits vs. certification audits https://advisera.com/27001academy/knowledgebase/surveillance-visits-vs-certification-audits/

These materials will also help you regarding audits:
- Preparing for ISO Certification Audit: A Plain English Guide https://advisera.com/books/preparing-for-iso-certification-audit-plain-english-guide/
- ISO Internal Audit: A Plain English Guide https://advisera.com/books/iso-internal-audit-plain-english-guide/