I've sold a website which was monetized with google adsense. Do I have to tell Adsense team about the same, because the domain is already transferred to the new owner ? If I have to inform, where do I do it ?
You should have removed your AdSense (and any other) ads before the transfer. You can explain to the new owner that they will need to get their own account but unless you never plan to use AdSense again on other sites you shouldn't close your account. You only get one account (unless you also qualify for a business account) so you don't want to close it. At minimum you should log in to your account and disable ads for that site. If the new owner violates their TOS you could have problems.