It's good to see you here in the Community, @k mac haulage.
Allow me to provide information about the Construction Industry Scheme (CIS) feature in QuickBooks Online (QBO).
Once you turn on the CIS feature, you can no longer turn it off. If you don't want to use it, you can disregard the option. You don't need to worry about turning on the feature since it doesn't affect your transaction unless you'll use it. You might want to learn more about CIS, feel free to read this article: CIS in QuickBooks Online.
In addition, you may want to set up value-added tax (VAT) in your QBO account. This helps you keep accurate records of the tax that you collect and pay.
Our doors are always open to help you again if you have any other concerns or follow-up questions about taxes.