To set up a customer tag based fee, you need to be on the Growth Plan with Shopify Plus.
In the app admin, click Create Fee. Or click View Fees if you want to edit an existing fee.
Under the Customer tags section, click Enable customer tags.
In the Update data access window click Update.
Click the Add customer tags.
Select the tags the fee should apply to. You can use the search field to find a specific tag.
Click Select in the modal.
Click Save.
This will apply the fee only to orders where the customers tags match the tags you choose for the fee.
Watch the following video to see the setup steps: