From 12 May, NHS COVID Pass letters for international travel are valid for 180 days from the date they are generated (which is usually the next working after they are requested). NHS COVID Pass letters issued between 7 December 2021 and 11 May 2021 are valid for 30 days. NHS COVID Pass letters issued before 7 December do not have an expiry date. However, your NHS COVID Pass letter should show your most up to date vaccination.