In the UK, English tests are used for visas such as the Skilled Worker visa and for registration with bodies such as the Nursing and Midwifery Council. Not every version of a test is accepted for every purpose.
These articles cover UK visa English requirements, IELTS for UKVI, and the English rules for nurses registering in the UK, with links to the official pages to check before you book.
OET C+ Writing for the NMC: what a score of 300 means, why a short letter can mean a resit, and how nurses can plan and practise a clinical letter for it.