One of our client are not using QB any more,but still they are our client. what will be the purposed solution to remove the client from our QB portal and from the billing

Let me provide the proper way of removing clients in QuickBooks, @Rubab.

If you're the current primary admin for your client's company, assign a new primary admin to remove the clients successfully. Then proceed to the steps below:

1. If the client is part of your ProAdvisor discount plan, remove them by going to the Gear icon and then Billing and Subscriptions.
2. Select the Your Subscriptions tab or the Accountant-billed Subscriptions tab.
3. Select the client you want to remove.
4. From the Select Action dropdown, hit Remove from Wholesale.
5. Then, Proceed to remove your client.
6. Go to the Clients menu.
7. Find the client you want to delete and select their name.
8. In the Edit client dropdown, select Delete permanently.
9. Select Yes to confirm.

If you're not the primary, proceed to remove your clients from the Billing and Subscriptions if they are part of your ProAdvisor discount plan. Refer to the detailed steps below:

1. Go to the Gear icon and then Billing and Subscriptions.
2. Select the Your Subscriptions tab or the Accountant-billed Subscriptions tab.
3. Select the client you want to remove.
4. From the Select Action dropdown, hit Remove from Wholesale.
5. Then, Proceed to remove your client.
6. Go to the Clients menu.
7. Find the client you want to delete and select their name.
8. In the Edit client dropdown, select Delete permanently.
9. Select Yes to confirm.

Check this article for more details on keeping track of clients and updating your client list: Manage clients in QuickBooks Online Accountant.

After removing the client, they can keep an external record of the data by exporting reports and lists to Excel. For detailed steps, please refer to this article: Export your reports to Excel from QuickBooks Online.

For additional references, while working with QBO, you or your clients can also open the topics from our help articles.

Feel free to reach out if you have any questions about billing or managing user concerns. I'm here to help. Take care.