So there it is not written that the new owner is OBLIGED to enter himself in the TCP. He can do it, but he doesn't have to. But when registering a vehicle, you either enter yourself or ask a traffic police officer. Although the latter do not want to do it. The topic is more of interest to people who are engaged in resale and they have to drive the cars they sell. They understand what I mean. I was recently stopped by a traffic police officer, he could not prove to me that I am obliged to enter myself into the TCP. But the signature of the previous owner is required.

GC
Article 456. Obligations of the seller for the transfer of goods
1. The seller is obliged to transfer the goods to the buyer, stipulated by the treaty purchase and sale.
2. Unless otherwise provided by the contract of sale, the seller is obliged, simultaneously with the transfer of the thing, to transfer to the buyer its accessories, as well as documents related to it ( technical certificate, quality certificate, instruction manual, etc.), statutory, other legal acts or an agreement.

Order of the Ministry of Internal Affairs of the Russian Federation, the Ministry of Industry and Energy of the Russian Federation and the Ministry of Economic Development and Trade of the Russian Federation dated June 23, 2005 * N*496/192/134
"On approval of the Regulations on passports Vehicle and vehicle chassis passports"
(as amended August 24, 2006, December 31, 2008, January 19, 2011)

Position
on vehicle passports and vehicle chassis passports
(as amended on August 24, 2006, December 31, 2008)

16. ... When changing the owners of vehicles or chassis, appropriate entries are made in the passports in compliance with the requirements provided for in Section II of this Regulation, which are transferred to the new owners or owners.
50. Sections located on the left front and reverse sides passports and containing information about the owners of vehicles and completed transactions aimed at alienating and acquiring ownership of vehicles ("Name (full name) of the owner", "Address", "Date of sale (transfer)", "Document on the right of ownership", "Signature of the former owner", "Signature of the present owner"), are filled in in the following order:
50.2. When making transactions in accordance with the established procedure aimed at alienating and acquiring ownership of vehicles:
in the lines "Name (full name) of the owner", "Address", the data of the new owner who acquired the ownership of the vehicle are indicated;
the line "Date of sale (transfer)" indicates the day, month and year of the transaction aimed at alienating and acquiring ownership of the vehicle;
the line "Document of ownership" indicates the name of the document confirming the ownership of the vehicle, its number (if any) and the date of compilation;
in the line "Signature of the former owner" the signature of the previous owner of the vehicle is affixed, and in the line "Signature of the present owner" - the signature of the new owner.

And in addition, about the sections that the traffic police fills

51. Details located on the left front and back sides of passports and containing information about the registration of vehicles or their removal from registration records("Certificate of registration of the vehicle, series, N", "State register sign", "Date of registration", "Issued by the traffic police", "Date of deregistration"), are filled in by officials of the departments of the State traffic inspectorate. The entries made are certified by the signatures of the indicated officials and imprints of the seals of the State Traffic Inspectorate.