I have a client who only wants to use QB Online Payroll Core without using QB Plus. They currently have both subscriptions but only need the payroll function.

Thanks for coming back, KRD62.

It seems like your client is using a bundle QuickBooks Online (QBO) subscription with payroll services. They can subscribe to a stand-alone payroll where they can choose a payroll plan right to their business. They can go to this link: https://quickbooks.intuit.com/payroll/pricing/bundle/. From there, they can select Core, Premium, and Elite plans. Then, choose the I only need payroll option where they continue with payroll only. 

Once they have the Payroll plan only, they can cancel their QBO subscription. Here's how:

1. Login to QBO and choose the duplicate account you wanted to cancel.
2. Go to the Gear icon ⚙ and then select Account and Settings.
3. Choose Billing and Subscription.
4. Under the QuickBooks section, click Cancel.
5. Follow the steps to cancel your account.

For the complete details on how to cancel your subscription, check out the Cancel your QuickBooks Online subscription or trial article. If they need assistance with canceling their QBO and Payroll Core accounts, they can contact our Customer Support Team. Here's how: 

1. Go to the Help icon on the top right. 
2. Enter your concern in the search field.
3. Choose Talk to a human.
4. Click the OK. To get you to the right human, in a few words, tell me what you need help with option and tap I still need a human. 
5. Press Contact us.
6. Tick Continue. 
7. Choose Get a callback.

To ensure we address your concern, our representatives are available from 6:00 AM to 6:00 PM on weekdays and 6:00 AM - 3:00 PM on Saturdays, PST. See our support hours and types for more details about this one.

Feel free to visit our Account management page for more insights about managing your Intuit product users.

I'm just one post away if you need anything else in QBO. Just add the details to your reply and I'll be there to address them for you. Take care always.