Great day and welcome to the Community, @ddornan. I'm here to guide you on how you can remove imported contact details so you can just use the contacts you've entered manually.
QuickBooks Self-employed doesn't have an option to import contact details. If you're trying to delete imported customers/suppliers in your QuickBooks Online account, you can make them inactive permanently instead. Here's how:
To make suppliers inactive
1. Click the Expenses tab on the left menu.
2. Select Suppliers.
2. Choose the suppliers you want to make inactive by checking the boxes.
3. In the Batch actions drop-down menu, select Make inactive.
To make customers inactive
1. Click the Sales tab on the left menu.
2. Select Customers.
2. Choose the customers you want to make inactive by checking the boxes.
3. In the Batch actions drop-down menu, select Make inactive.
You can also merge accounts, customers, or suppliers if you want to have a single representation in your Chart of Accounts or in your financial reports. To learn more about it, read through our help article: How to Add, Delete, Merge, and Restore a Customer.
Let me know if you have anything else in mind. We're always happy to assist. Cheers!
