You should write ‘first-class honours’ under the degree you received the grade for.
There are two ways you can write first-class honours:
1. Write it out in words (‘first-class honours’):
Hull University, 2019 – 2022
BSc (Hons) Economics
2. Express it in numbers (1st):
Bangor University, 2018 – 2021
BSc (Hons) Business Management (1st)
First-class honours is the highest grade classification you can receive for an undergraduate degree in the UK. Similar CV formatting rules apply if you got upper second-class honours, lower second-class honours, third-class honours, or an ordinary pass.