Is AV required for a new iMac?

It is NOT recommended to install any third party antivirus.

Read this excellent article about keeping your mac secure:

Effective defenses against malware and other threats: https://discussions.apple.com/docs/DOC-8841

fishybez wrote:

I'm looking to buy a new iMac 24". Is there a need to install AV, or are the inherent security features adequate? If AV is required, does the community have a recommendation?

Third party AntiVirus is not recommended— it typically does nothing but add issues to the macOS and competes directly with Apples own built in security:

macOS - Security - Apple https://www.apple.com/macos/security/

Apple Platform Security - Apple https://support.apple.com/guide/security/welcome/web

more—https://manuals.info.apple.com/MANUALS/1000/MA1902/en_US/apple-platform-security-guide.pdf