This practice note discusses the grounds for varying a public contract within the scope of the Public Contracts Regulations 2015 (SI 2015/102), as amended by the Public Procurement (Amendment etc.) (EU Exit) Regulations 2020 (SI 2020/1319), without triggering the requirement to run a fresh procurement procedure. It also looks at the potential implications of unlawfully varying a public contract, and some practical ideas for how to minimise the difficulties associated with variations.