If we only use QuickBooks online for payroll (core), do we need to pay the subscription for Simple Start?

Your confusion ends here, @tmbartko.

Yes. Once you subscribe to payroll in QuickBooks Online (QBO), you'll still need to pay for your QBO Simple Start subscription. Though they have different subscriptions, the payroll plan is supplementary to your QBO plan.

If you haven't subscribed to the payroll service in QBO yet, you can visit this website: https://quickbooks.intuit.com/payroll/pricing/. Then, select the Core plan.

Once you're ready to get started on your payroll setup, you can read through this article: Get started with QuickBooks Online Payroll. This helps you set up your new QuickBooks Online Payroll Core.

It's nice working with you, @tmbartko. Feel free to visit us again if you need further assistance managing payroll in QBO. We're always here to help you.