[16] In August 2020, Cox scored his maiden century in first-class cricket against Sussex at Canterbury in the second round of matches of the 2020 Bob Willis Trophy.
Cox went on to finish the innings unbeaten on 238 in a Kent record partnership for any wicket of 423 runs with Jack Leaning.
[24] He was part of the Oval Invincibles squad for the 2021 season of The Hundred, having been selected in the Wildcard Draft in the run up to the start of the competition.
In December 2021 he was recruited by Big Bash League side Hobart Hurricanes as a replacement for the opening match of their 2021/22 season.
[27][28] In September 2022, Cox was one of five uncapped players named in the England squad for their seven-match Twenty20 International tour of Pakistan later in the same month.