It is currently not possible to move external domains from one contract to another.
If you want to use an external domain that you have already set up with IONOS on a different contract (e.g. because you now want to use the domain with a different product), unfortunately you have to remove the external domain from our systems and set it up again in the selected contract.
If you remove the domain from one contract, it can take multiple hours before the domain is removed from our systems and can be set up again.