Can I add fields in customer profile in QB Online Plus?

Hello there, @alibhai-mustafa.

Currently, we're unable to add a custom field in the customer's profile in QuickBooks Online (QBO). Instead, we can use the Notes or Attachments.

Here's how:

1. Go to the Sales menu, and then choose Customers.
2. Find the customer on the list, and then click the name.
3. Click the Edit button in the upper right-hand corner.
4. On the Customer information page, go to the Notes or Attachments section.
5. Enter the customer's additional details.
6. Click Save once done.

I've added this article about managing customers in QBO: Add and manage customers in QuickBooks Online.

Drop me a comment below if you have other questions. I'm more than happy to help. Take care!