I asked to open the topic so that I could answer the question myself - I hope it will be useful to someone someday.
After searching, I found the content of the relevant act:
ACT of January 20, 2005 on the recycling of end-of-life vehicles.
I am just citing paragraphs that interest someone who sells a vehicle for parts:
Chapter 1
general rules
Art. 1.
1. The Act defines the rules for dealing with end-of-life vehicles in a manner that protects human life and health, and protects the environment in accordance with the principle of sustainable development.
2. In matters relating to the handling of end-of-life vehicles in the scope not regulated in the Act, the provisions on waste shall apply.
Chapter 3
Vehicle Ownership Responsibilities
Art. 18.
The owner of the end-of-life vehicle may hand it over only to the entrepreneur running the disassembly station or the entrepreneur running the vehicle collection point.
Art. 19.
The owner of the end-of-life vehicle or a person authorized by him, when handing the vehicle over to the entrepreneur running the disassembly station or the entrepreneur running the vehicle collection point, is obliged to show:
1) ID card or other document confirming identity;
2) the vehicle registration certificate and the vehicle card, if it was issued, or another document confirming the data contained in the registration certificate;
3) proof of ownership in the case of the owner of the vehicle other than that entered in the registration certificate.
Art. 20.
The owner of the end-of-life vehicle is obliged to submit an application for deregistration of the vehicle within 30 days from the date of receipt of the certificate of disassembly of the vehicle or the certificate of acceptance of an incomplete vehicle.
Chapter 4
Obligations of entrepreneurs operating disassembly stations
Art. 23.
1. The entrepreneur operating the disassembly station is obliged to accept each end-of-life vehicle that has the vehicle identification features referred to in Art. 66 sec. 3a point 1 of the Act of June 20, 1997 - Road Traffic Law, subject to paragraph 7.
2. The entrepreneur operating the disassembly station, when accepting the end-of-life vehicle, may charge a fee from the owner of the vehicle, subject to paragraph. 3 and 6.
3. The entrepreneur running the disassembly station does not charge the fee referred to in sec. 2, if the following conditions are jointly met:
1) the vehicle is registered in the territory of the country, in accordance with separate regulations;
2) end-of-life vehicle:
a) is complete,
(b) does not contain other waste that does not come from the vehicle.
4. A complete vehicle is considered a vehicle that contains all essential elements and its mass is not less than 90% of the vehicle mass.
5. In the case of accepting an incomplete end-of-life vehicle from the owner, the fee referred to in sec. 2, may not exceed the amount of PLN 10 per 1 kg of missing vehicle weight.
7. The entrepreneur operating the disassembly station may refuse to accept an incomplete vehicle, if the owner of the vehicle refuses to pay the fee referred to in sec. 2.
8. The minister responsible for transport, in consultation with the minister responsible for the environment, taking into account the requirements of environmental protection, the need to ensure the completeness of vehicles in order to obtain the appropriate levelsrecovery and recycling and counteracting the improper management of waste, shall determine, by regulation, a list of essential elements of the vehicle referred to in paragraph 1. 4.
Art. 25.
1. In the case of accepting a vehicle that does not meet the conditions specified in Art. 23 sec. 3 point 2 lit. a, the entrepreneur running the disassembly station is obliged to issue a certificate of acceptance of the incomplete vehicle. The provisions of Art. 24 sec. 1 point 1 and sec. 2-4 shall apply accordingly.
Chapter 8
Penal provisions
Art. 48.
Who, contrary to the provision of art. 18 does not transfer the end-of-life vehicle to the entrepreneur running the disassembly station or the entrepreneur running the vehicle collection point, shall be punishable by a fine.
Art. 50.
Who, apart from the disassembly station, performs:
1) removal from end-of-life vehicles of hazardous elements or substances, including liquids,
2) dismantling from end-of-life vehicles items of equipment or parts suitable for reuse,
3) dismantling of elements suitable for recovery or recycling from end-of-life vehicles
- is punishable by a fine.
My comment on this - in general, the Polish state makes it impossible to sell cars for parts on its own, and even to take out parts for your own use.
Of course, there are also laws on environmental protection, etc. etc ....
And what should I do when I have the opportunity to buy a car body in perfect condition, it would be enough to change the drive and deregister the old shack ...?