Can social security bought from other provinces be moved back to the place where the household registration is located? What kind of formalities do you need to go through?

Yes, you can first issue an acceptance certificate at the social security center where your account is located, go back to the original social security unit for transfer-out procedures, and then go back to the social security center where your account is located for transfer-in procedures. You can also wait until the national social security network is connected, and the procedures may be simplified. The original social security unit will keep your social security account for you free of charge.