I created a Amazon AWS EC2 instance under my account and made an website/ftp on it, now a new partner wants to move the instance under his company account so his company can pay
This is not possible.
AWS Support does not have access to copy Amazon EC2 resources or manipulate any configuration options in AWS accounts. You can't separate an AWS account from an Amazon.com account or transfer resources between AWS accounts. It is possible to manually migrate Amazon EC2 resources from one account to another by completing the steps described here.
Source : https://aws.amazon.com/premiumsupport/knowledge-center/account-transfer-ec2-instance/