Hello CharlotteM,
Thanks for posting on the Community.
The correct way to remove the account for a subscription which will no longer be used is to sign into your QuickBooks Accountant profile and go to the Cog Wheel > Subscription & Billing > Your Subscriptions > Select the drop-down on the right-hand side of the client and select the option to 'Transfer billing to client'. This then prompts the client to subscribe upon sign-in and the account will expire if no billing details are entered.
After this, you can remove them from your client list by going to Clients > Select drop-down beside client > Make inactive.
Thanks!