This practical guidance relates to the Procurement Act 2023 regime As of 24 February 2025, the main provisions of the Procurement Act 2023 (PA 2023) are in force. Procurements begun on or after this date must be carried out under PA 2023, whereas those begun under the previous legislation (the Public Contracts Regulations 2015 (PCR 2015), SI 2015/102, the Utilities Contracts Regulations 2016, SI 2016/274, the Concession Contracts Regulations 2016, SI 2016/273, and the Defence and Security Public Contracts Regulations 2011, SI 2011/1848) must continue to be procured and managed under that legislation. This practical guidance is about vertical and horizontal public procurement under PA 2023. For background reading, see Practice Notes: Introduction to the Procurement Act 2023—PA 2023 and Procurement Act 2023 transitional and saving arrangements—PA 2023. For practical guidance on vertical agreements (previously known as ‘Teckal’ or ‘in-house’ agreements) and horizontal agreements (previously known as ‘Hamburg’ or ‘co-operation’ agreements) under PCR 2015, see Practice Note: The ‘in-house’ (Teckal) and ‘co-operation