This Practice Note examines the law and practice in relation to anonymisation, pseudonymisation and privacy enhancing technologies (or PETs). In particular, it looks at the requirements for effective anonymisation and pseudonymisation and an explanation of some basic techniques that may be used. This Practice Note also provides an introduction to the area of technologies known as PETs. The Practice Note considers the position under the United Kingdom General Data Protection Regulation, Assimilated Regulation (EU) 2016/679 (UK GDPR) and the UK Data Protection Act 2018 (DPA 2018). It does, however, consider EU case law and guidance where relevant to the position under the UK GDPR. For information on the position under the EU’s General Data Protection Regulation, Regulation (EU) 2016/679 (EU GDPR), see Practice Note: Anonymisation, pseudonymisation and privacy enhancing technologies (PETs) in the EU. There are critical points of divergence between the position under the UK GDPR and the position under the EU GDPR on this particular topic. Note, on a general level,