If you need to transfer a domain between AWS accounts, you cannot do a standard domain transfer. This might seem annoying at first but when you realize how easy it is to do, and you don't have to pay a transfer fee, you will be happier for it.
Open Up AWS CloudShell in the Source AWS Account
//run the follow command in AWS CloudShell
//1234567890 is the AWS Account Id for the Destination Account
aws route53domains transfer-domain-to-another-aws-account --domain-name example.com --account-id 1234567890
//Result Should Provide a Password
{
"OperationId": "a2d287c3-401b-4f53-a506-13b70ec21803",
"Password": "TRx/:37ep+:SmvmD"
}
Open Up AWS CloudShell in the Destination AWS Account
//run the follow command in AWS CloudShell
//use the password from the above command
aws route53domains accept-domain-transfer-from-another-aws-account --domain-name example.com --password "TRx/:37ep+:SmvmD"