Under the UK GDPR, you must appoint a DPO if:
you are a public authority or body (except for courts acting in their judicial capacity);
your core activities require large scale, regular and systematic monitoring of individuals (for example, online behaviour tracking); or
your core activities consist of large scale processing of special categories of data or data relating to criminal convictions and offences.
This applies to both controllers and processors. You can appoint a DPO if you wish, even if you aren’t required to. If you decide to voluntarily appoint a DPO you should be aware that the same requirements of the position and tasks apply had the appointment been mandatory.
Regardless of whether the UK GDPR obliges you to appoint a DPO, you must ensure that your organisation has sufficient staff and resources to discharge your obligations under the UK GDPR. However, a DPO can help you operate within the law by advising and helping to monitor compliance. In this way, a DPO can be seen to play a key role in your organisation’s data protection governance structure and to help improve accountability.
If you decide that you don’t need to appoint a DPO, either voluntarily or because you don’t meet the above criteria, it’s a good idea to record this decision to help demonstrate compliance with the accountability principle.