From the 30th November 2019, the minimum weight requirement to register a drone with the CAA is 250 grams. If you are flying a drone like the DJI Mavic Mini, you might not need to register because it weighs just 249g. However, you still require qualifications for commercial drone use. Make sure you know the rules and consult the Drone Code before you fly, and if you want to fly commercially, you need to take the PfCO CAA exam (Permission for Commercial Operations).