The extra precautions that need to be taken when you need to send (or make accessible) personal information to other organisations located outside the UK, can be confusing.
The ICO has updated its brief guide to help make it easier to comply with the rules and, if this applies to you, we recommend you have a look at https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/international-transfers/a-brief-guide-to-international-transfers/.