Depending on the final intention, one of the following paths may be taken
If the intention is to permanently close the RIA account, please start a new application as a Family Advisor or Non-Professional Advisor account. Once opened, submit a request to IBKR to have your existing clients move under the newly opened Family Advisor or Non-Professional Advisor account structure.
If the intention is to allow the registration to expire but maintain the account title as is, remove the CRD number from the existing account. Once completed, the account will automatically downgrade to a Family Advisor or Non-Professional Advisor account.