ATF
Authorised Treatment Facility, for vehicles
The short answer
A permitted site that depollutes scrap vehicles and issues the DVLA Certificate of Destruction. A different scheme from an AATF, and a different certificate.
In practice
The two get confused because the initials nearly match. An ATF deals with end-of-life vehicles and its certificate tells the DVLA a car has been destroyed. An AATF deals with electricals and its evidence note settles a producer's recycling obligation. Neither is the certificate of destruction a shredding company gives a customer for confidential material.