There are two types of registration: one is for the operator/owner of the UAV, and another registration is for the drones themselves.

If your drone weighs less than 250g and meets the conditions mentioned below, you as a UAV operator/owner DO NOT need to register.

If your drone is over 250g, then registration is required - registration is done in the EU member state in which you reside, and for Bulgaria this is done at https://drones.caa.bg

Registration is one-time, regardless of how many drones you will operate in an unlimited or specific category.
There is also a third type of procedure - pilot certification. You need to be certified if, for example, the drone falls under subcategory A1/A3 - read here

You need to register as an operator/owner if your UAV:

  1. weighs less than 250 g, has a camera or other sensor capable of capturing personal data and does not have information in its documentation to comply with the Toy Directive 2009/48/EC.
    • example: DJI Mini 2,3
  2. weighs more than 250 g
    • Any drone that weighs 250g or more.

You do not need to register as an operator/owner if your BLS:, if your UAV:

  1. it weighs less than 250g and has no camera or other sensor capable of capturing personal data.
    • Any drone under 250g, no personal data sensors/no camera.
  2. is a children's toy (this means that its documentation shows that it complies with the Toys Directive 2009/48/EC), regardless of whether it has a camera or other sensor and weighs less than 250g
    • example: DJI Tello

Drone registration

Unless certified, unmanned aerial systems (UAS/UAV), also known as drones, do not need to be registered.
The drone is certified when it has a certificate of airworthiness issued by the Bulgarian aviation authoritiy which is the General Aviation Administration (see caa.com). In this case, registration is required. A certified drone is only required when the risk of the operation requires it. UAV certification is not required for operation in the unrestricted category.

Similar article: I bought a DJI Mini weighing 249g, do I need to be registered in Bulgaria?

Source:  drones.caa.bg