A controller determines the purposes and means of processing personal data. A processor is responsible for processing personal data on behalf of a controller. If you are a processor, the GDPR places specific legal obligations on you; for example, you are required to maintain records of personal data and processing activities. You will have legal liability if you are responsible for a breach. However, if you are a controller, you are not relieved of your obligations where a processor is involved – the GDPR places further obligations on you to ensure your contracts with processors comply with the GDPR.