Where do you set up a custom sales tax rate in QuickBooks Online?

Setting up a custom sales tax rate in QuickBooks Online is done in the Sales Tax center. This is the dedicated area within QuickBooks where users can manage all aspects of sales tax, including creating new tax rates, configuring existing ones, and setting up sales tax groups or agencies.

Using the Sales Tax center provides a streamlined and focused interface specifically designed for handling tax-related settings, making it the most logical place for this task. In contrast, the other options, such as the Settings menu, the Invoicing tab, and the Vendors tab, do not provide direct access or functionality specifically tailored for sales tax configuration. Therefore, the Sales Tax center is the correct and most efficient choice for setting up custom sales tax rates.