It depends on which microchip company it is. But most of them charge the fees for extras that no one really needs but they dont delete the chip info from their database if the pet owner doesnt
buy the extras. The one we used at the clinic (Home Again) told us that once the microchip is entered in the database it stays there forever regardless. I would suggest contacting your specific chip compsny and ask their policy.
When a dog or cat is microchipped
thr client is given some paperwork that includes a Way to access the pet's account at that microchip company so the client can update the contact info.
If you all dont have that paperwork, (you lost it or adopted a pet that is already chipped but came without the paperwork) you contact the microchip company. Most of them have a policy for that. At Home Again they need to try to contact the owner. If that owner doesnt respond to them, then they register the chip to you.
At least that's what their policy was up to 2.5 years ago when I retired.