Account migrations

It really depends on what resources and services you are going to migrate. Without knowing the detail, it's hard to tell if the migration can be seamless or not. Also are you going to migrate to another account that is still in the same AWS Organization? Things could get even more complicated if the target account is in another organization. Please refer to this blog post. https://aws.amazon.com/blogs/architecture/migrate-resources-between-aws-accounts/