The fast pace of change in maritime autonomy demands updated and relevant guidance for those owning and operating Maritime Autonomous Surface Ships (MASS). The Maritime UK Autonomous Systems Regulatory Working Group (MASRWG) published the first code of practice to global industry-wide acclaim in November 2017, with the second version following in November 2018. Whilst not a legal text, the Code has been used by manufacturers, service providers, and others as part of their day-to-day work. Many manufacturers have reported clients requiring compliance with the Code as a basis for contractual negotiations.Previous versions were focused on the design and manufacture of vessels, the operation of autonomous vessels, and a particular focus on skills and training. Version 3 of the UK Industry Code of Practice demonstrates UK’s continued leadership on autonomy with new sections on inland waterways. There is also an enhanced section on the principles that should underpin the design, manufacture and operation of autonomous vessels This version replaces the Code of Conduct (2016) and Version 2 of the Code of Practice (2018).