Please Note: If you have different rates for delivery fees then they need to be created as non-inventory items and you must use a different name other than "Delivery Fee' specifically. You can name it "Fee for Delivery".
Question:
How do I create a taxable flat delivery fee?
Answer:
Enable the Taxable Delivery Fee
The flat delivery fee toggle is found under Configurations > Config Page > Delivery > Delivery Order Requirements
Set your Delivery minimum
Choose subtotal or grand total to calculate the minimum
Set your Delivery Fee
Toggle the Taxable Delivery Fee to on
Adding Taxable Delivery Fee to Tax Rate
Navigate to Configurations > Config Page > Taxes > Point of Sale Tax Setup
You may need to first identify which tax-rates should apply to the Delivery Fee, by discussing this with your local tax expert.